- Estimated achievement difficulty: 6/10
- Offline achievements: 12 
- Online achievements: 0
- Approximate amount of time to 200: 1-3 hours
- Minimum number of playthroughs needed: 1
- Number of missable achievements: None!
- Glitched achievements: None!
- Do cheat codes disable achievements: No Cheats
- Does difficulty affect achievements: No
Alien Hominid HD isn't an overly hard game to complete. There are a few achievements that could take several tries to earn. The game would be easier if it wasn't for the "WMD" and "Head Chomper" achievements which can be tough and time consuming.
Welcome to Alien Hominid HD! A rather fun game, Alien Hominid will require at least 1 playthrough plus the playing of two or three levels or mini games to collect all of the achievements. There are no cheats to help you out, either.
When earning the campaign achievements, it's best to start playing on the Easy difficulty. The two achievements for completing the game on the Medium and Hard difficulties can be earned by replaying the final boss fight on either of those difficulties for their respective achievements. Playing on Easy will also make earning some of the other achievements slightly easier.
Some achievements will come through natural game progression. Like the first achievement "Alien in Training". From the start of the first level, you should destroy every building that you see so you don't have to go back and try for your "City Destroyer" achievement. You'll unlock it when you destroy your 25th building. When you reach level 2-2, be sure to eat 50 KGB agents for your "Hungry Yeti" achievement. If you can survive in one game long enough, you'll earn your "Killing Spree" achievement and using a guide, you can unlock most of the hats for the "Mad Hatter" achievement. You won't have it at the end of your first game as some hats require playing certain levels on different difficulties to unlock them. The "Head Chomper" achievement is best left until after you complete the game as you can die very easily while attempting it.
When you're finished with your first playthrough, simply re-load the final boss fight on the Medium and Hard difficulties for the "Adult Alien" and "Expert Alien" achievements. Now is also the time to re-play any missions on different difficulties for the hats that you need to unlock Mad Hatter.
Once all of your other achievements are completed, the only ones that should be left are "WMD" and "Survivalist". Since you should now have all of the mini-games unlocked, you can follow the guide on the best way to earn those achievements.
Without a doubt, the hardest achievements in the game are "Head Chomper" and "Expert Alien". With some practice and a little luck however, you should be able to earn them. If you missed any achievements, simply follow the achievement guide and re-load the level where the achievement can be unlocked.
[XBA would like to thank Skillet for this Roadmap]