🏆100% Achievement Guide for Serious Sam 2

To obtain all achievements, you need to:

• Complete the game on Serious difficulty
  
• Complete the game with Enemy multiplier set to 2X or higher, on any difficulty
  
• Beat all levels under the estimated time (these time limits are VERY generous).
  
• Find 60 secrets in the campaign
  
• Complete the final level on Serious difficulty, without dual weapons, sprinting and rocket jumping

All achievements can be completed in 1-2 playthroughs, which should take about 15 hours. Step 1. Start a new campaign on Serious difficulty. Set the Enemy Multipler to 2x or higher. Complete only the first level.
Step 2. Start a new campaign on Serious difficulty. Complete the entire game. Find secrets on this playthrough (see Active Achievements section).
Step 3. Complete the last level on Serious difficulty, this time with dual weapons, sprinting and rocket jumping disabled.
DISCLAIMER: Disabling doesn't mean simply unbinding the keys. It is recommended to disable these three features in the custom settings as a whole. If you do not have the settings disabled, and you get hit by blast damage (AOE) by your own Rocket Launcher, the game will count that as rocket jumping, and the achivement (Mental Institution Master) will get voided, and you'll have to re-play the longest level again.
Step 4. Start a new campaign on Tourist. Set the Enemy Multipler to 2x. Complete the game, where your focus is to go as fast as possible.

• Remember to save often, both quick saves and slow saves. If you die, you return to the last saved location, which sometimes can be 5-15 minutes of progress
  
• Get comfortable with dual wielding weapons. It is a significant damage buff (on PC usually bound to Z)
  
• Remember there are Hand Grenades (on PC usually bound to M3)
  
• You can track achievement progress under Extras -> Achievements.

These achievements should be obtained by simply playing the game. Note that these achievements exist, and continue to the next section. If you do not obtain these achievements passively, I recommend playing the last level with a high Enemy Mulitplier and low difficulty. Ammunition scales with Enemy Multiplier, meaning more grenades, birds etc.

All active achievements are related to finding secrets. In this guide, I will refer to secret locations using timestamps from the video below. If you prefer a written guide, I will also inform you the Level name and # secret it corresponds to in the written guide. The achievements are written in order of appearance in the game, so just start from the top.

https://steamcommunity.com/sharedfiles/filedetails/?id=129738470
Thank you to the original creators of these guides for putting everything together.

At this point, you should have all campaign and story related achievements. If you've completed all the achievements, congratulations!
If not, I've collected the "most missed" achievements here:

Other Guides
We’ve made more guides — all built on the same principles:

• At least one of us has 100%'ed the game
  
• This guide is built for speed and efficiency
  
• We might cheese. We do not cheat
  
• If the game has a story → there will be spoilers
  
• This is our route to reach 100% as fast as possible
  
• We’re open to feedback and better methods, but we can’t always test them ourselves once we’ve already completed the game

Find all our guides here:
LaBoeg or Lamone