The Comprehensive Gear Up Achievement Guide

To start with, Gear Up currently has a total of 27 achievements, which can be broken down into 3 sets:

• Kill-related achievements, where we need to shoot stuff

• Gamemode-related achievements, where we need to play different modes

• Miscellaneous achievements, that don't fit the other two categories

There are a total of 14 kill-related achievements in Gear-Up. One thing they all have in common is they require you to get kills (duh). What this means is that you need to find a populated lobby (or get a friend to help you) if you want to get them.

You get a kill when you destroy someone with either your main gun or with your supports.
Some people mentioned that assists also count as 'kills' for the achievements but I haven't been able to confirm that. Environmental kills (ie desserting/drowning) and self-destroys do not count. None, all require player interaction. I remember having seen bots in this game way long ago (2017-2018) and I remember that you had to have bought the premium version of the game to make them spawn, but I can't find any mention of that anymore, either on the store page or in-game. Hypothetically, if bots still exist, all the following achievements can easily be done solo. All except 1 (Royal Straight Crush). Create a lobby and have your friends go into the opposite team as you. Then, unleash hell onto them. Because you are not alone in the lobby you will also earn G, useful for unlocking the Grayhound saw.

These achievements track lifetime kills, so progress is carried over games.

Destroy 10 enemies with the default starter cannon.
(It's called "Cannon Basic" in-game). While it packs a decent punch, its quite tricky to use. Avoid close-quarters engagements and engage from the medium ranges. Destroy 20 enemies with the Grayhound (saws).
A saw-spewing weapon with extremely good damage. Get as close and personal as you can and keep firing. Avoid long-distance engagements. Keep in mind it costs 6G to unlock, so earn some of it first! Killed a deserting enemy
Basically kill someone while they are out of bounds. If they die from being out-of-bounds and not by you it won't count. Destroy 25 enemies. Destroy 50 enemies. Destroy 75 enemies. Destroy 100 enemies. Destroy 1500 enemies.
Yep, its pretty grindy. Here are some tips if you are planning to farm towards these:

• Start a game on Conquest/TDM (because those modes have specific spawnpoints).
  
• Make sure all the "targets" to be farmed are placed on the opposite team than you.
  
• Make your way over to the enemy spawn and start destoying the enemies as soon as they spawn (there is no spawn protection).
  
• For TTK optimisation, make sure the "targets" have as little HP as possible. You can lower your health by equipping the Flea legs, the Scout hull and the Hidden turret for a measly 40HP. Oh and remove any supports that increase armor.
  
• Try to pick a gun that does more than 40dmg per shot so that you can oneshot. I recommend avoiding snipers and shotguns however, as the former has low ammo and firerate and the latter limited range. The greyhound saw (paired with a couple machinegun supports) is also a valid alternative.
  
• In case you run out of ammo, there is often an ammo pickup near all spawns, make your way over there.
  
• From testing, this setup yields around ~60-70 kills per 10mins with 1 enemy target and around ~70-90 kills per 10 mins with 2 enemies. Having more targets means higher amount of kills per minute, but the sweet spot seems to be around 2-3 targets (because of diminishing returns and the difficulty of getting more people in-game).

These achievements' progress is reset when a round ends, so make sure to complete them within 1 game round.

Destroy at least seven different opponents in a team game mode.
This one is a little difficult. You need to find a lobby with enough players (more than 13) AND is playing either Conquest, TDM or Tag AND kill almost every single enemy once before the round ends.
It is possible to complete this with a lobby of just 7 others by killing each of your (4) opponents once, teamswitching, and killing your (3) ex-teamates for a total of 7 'unique' kills. I haven't confirmed the latter method, but it might be worth a try if you can't find a full lobby. This method is confirmed to work. 2 kills in a row
A killstreak achievement. Get kills and, if you die or the round ends, the streak resets. Try to play more defensively and don't hesitate to retreat/seek your team's help if you are at a disadvantage. The same applies to all the following killstreak achievements. 3 kills in a row 4 kills in a row 6 kills in a row 10 kills in a row

There are a total of 8 gamemode-related achievements in Gear-Up. They mostly revolve around winning rounds and completing objectives, sometimes with your team.

• In Deathmatch, you win if you have the highest score when the round ends. If there is a tie the person whose name is first in alphabetical order wins.
  
• In TDM, you win if your team has more kills than your enemy. If there is a tie, noone wins.
  
• In Conquest, you win if your team has more points than the enemy when the timer ends OR if your team reaches max score (usually 1 000 or 100). If there is a tie, noone wins.

6 of them can be done solo, the rest require more players. All except 1 (Massive Attack). See below for tips.

These can all be achieved naturally by playing the game. Below are the strats for those who want to speed-up the process.

Win 20 deathmatch rounds.
This one is simple. Host a new deathmatch game, set the timer to 1 minute (to be as fast as possible) and start. Because you are the only one in-game, when the round ends you will be first, even with 0 kills. Keep going until the achievement pops up. Don't AFK or you will be kicked for inactivity, so move around a bit. Est. time to completion: 25mins Win 20 team deathmatch rounds.
More complex than the previous one, but still easy. Host a new team deathmatch game, set the timer to 1 minute and start. In order to win, however, you need score, otherwise the game will end in a draw. Luckilly, deaths count towards the enemies' score so drive into the sea / out of bounds and die, then switch teams. Your new team will now win. Don't AFK or you will be kicked for inactivity, so drive around a bit. Est. time to completion: 25mins Win a TDM round overwhelmingly, with a ratio of 4:1 or higher.
Essentially, you need to win a TDM round with at least 4 times bigger score than the enemy. Follow the steps above (TDM Veteran) and you will get this easily.

Similarily, all these can be achieved naturally by playing the game. Below are the strats for those who want to speed-up the process.

Win 3 conquest rounds.
Host a new conquest game, set the timer to 1 minute and start. Find a way to die (drive into the sea / out of bounds or self-destruct) then switch teams. Your new team will now win. Avoid trying to win by capturing points, because 1 person capturing takes 1 minute (You could increase the time limit to 2 minutes but that would double the time you need to play). Don't AFK or you will be kicked for inactivity, so drive around a bit. Est. time to completion: 5mins Win 20 conquest rounds.
Same as 'Conquest Victorious' but 17 more times Est. time to completion: 25mins Win a Conquest round overwhelmingly, with a ratio of 4:1 or higher.
Essentially, you need to win a TDM round with at least 4 times bigger score than the enemy. Follow the steps above (Conquest Victorious) and you will get this easily. For a "more legit" way, start a 10 minute conquest match, capture all the points and wait for the victory. Capture a conquest tower together with 3 or more teammates.
Self-explanatory. The achievement unlocks when the tower is captured, so make sure everyone is inside the capture radius at that moment. The minimum amount of people in a lobby required for this is 7 (4 on the achieving team and 3 on the enemy team for balance). Assist in capturing at least 20 conquest towers in a single round.
This is tricky. If there is noone in your team to help you capture, time will run out, even at 25 minutes before you get 20 captures. If there is noone in the opposing team to decapture the points you captured, the game will end by points before you get 20 captures. To do this, get two friends, one in your team, the other in the enemy team and start a match with the maximum duration of 25 minutes. Go around the map in circles capturing points together while the 'enemy' follows you around and decaptures the point once you are done. Repeat until complete.
This can be done in random lobbies, but only during a high intensity game where no team has a clear advantage and capture points keep trading hands.

There are also 5 achievements that don't fit any of the above sets. They mostly revolve around healing, tanking damage and not playing the game. :)

Only 2 of them can be done solo, the rest require at least 1 more player. All of them.

Drown in the water at least once.
Drive into deep enough water and drown. Make sure the map you are spawning in actually has deep water and that you aren't using any propulsions that make you float over water Repair 20000 armor in lifetime.
Play as a medic! In order to heal you will need to use either the repair cannon (costs 6G) or the repair gun supports (costs 5G). Healing yourself doesn't count, either with the auto repair suppport, or with splash healing from the aforementioned guns. Should be noted that healing enemies counts towards this achievement. Repair (1250) armor in one round of a team game mode.
Again, play as a medic and try to heal as much as possible. The bigger the game duration, the better chance you got to get this one. Make sure to play Conquest or TDM. Recieve 500 damage without being destroyed in a round.
This achievement is slightly misleading. What it actually wants is "Receive 500 damage in a single life", the "without being destroyed in a round" part is not necessary. So, get a teamate to act as a medic for you and keep you alive. If you die you can try again. Keep in mind that self-damage doesn't count towards this. The easiest way to get this is to get a friend to damage you while you go around and pick up health packs (or heal yourself with splash healing from your own repair guns).
Also yes, this achievement has a typo. Back playing after more than one week of Gear Up absence.
Simple in theory: stop playing and come back in more than a week. This might be hard if you really like Gear Up. The only requirement is that you come back after more than one week of abscence: 1 week + 1 second, 2 ½ months or 3 years, you will still get it! Keep in mind that you have to join a match for the achievement to pop up, just opening the main menu doesn't count.

The following achievements no longer exist but used to exist at some point in the past. They are currently unavailiable and thus, unachievable. Here you will also find any changes regarding the achievements.

You have played the Gear Up alpha version
This achievement was gived to all those who played the alpha version of Gear Up. Renamed to 'Early Adopter' and hidden around the end of 2014/start of 2015. Deleted in mid 2015. NOT IMPLEMENTED
Deleted between 2013/2014. NOT IMPLEMENTED
Deleted between 2013/2014. Destroy 100 bots.
Unlocked by killing 100 bots. Deleted in August/September 2016. Destroy at least seven different opponents in a team game mode.
Was Renamed to Royal Straight Crush around the end of 2015/start of 2016. Recieve 1000 damage without being destroyed in a round.
This was changed from 1 000 damage to 500 around the end of 2014/start of 2015. Repair 30000 armor in lifetime.
This was changed from 30 000 armor to 20 000 in August/September 2016.

Here you will find a comparison between the old icons for the achievements, from newest to oldest.

Thanks for reading this far! I hope that this guide has helped you get those achievements that you are missing! If there is a problem / I missed something or you have a suggestion, don't hesitate to leave a comment.

Happy achievement hunting!

Sources:

Another great achievement guide, sadly not in English. It was what inspired me to write this guide.
https://steamcommunity.com/sharedfiles/filedetails/?id=489855593

An awesome guide detailing the ins and outs of Gear Up. Used as a reference for general weapon tips.
https://steamcommunity.com/sharedfiles/filedetails/?id=561664159

For double-checking achievements.
https://www.chaptercheats.com/cheats/pc/147616/Gear-Up-Cheats.htm

For obtaining the old achievement thumbnails (huge thanks to those who crawled the page years ago!).
https://web.archive.org/web/*/http://steamcommunity.com/stats/GearUp/achievements/

Guide image by me.

:)