Bad and not very good game. but fairly easy 100% for little money

Will just list the most troublesome achievements and best approach on how to get all of them the fastest

1. Controller is easier so potentially do that
2. USE THE ZOOM check help for keybinding. Makes it all much easier

Note: It might be easier to do the 100.000 points achievement by grinding in story mode. I just did it in score attack mode

• Fly & Chew Gum - Perform a double abduction.
  
• UFO Pilot in Training - Abduct a cow.
  
• We're Gonna Need a Bigger UFO - Abduct 50 Earthlings in one game.
  
• Assassin - Smash 3 Earthlings with one dropped object.
  
• Alien Hero Extraordinaire - Complete the Story Mode.

1. Do the story mode
2. Do score attack

1. Do the tutorial on the moon
2. On the Farm level you need to do 2 things
Directly after doing objective 2 (kill 5 birds). Keep killing 50 birds until you get

Achievement
Bugs on a Windshield
Splatter 50 flying creatures in one game.

Next complete the level without dying

Achievement
Farm Warrior
Complete the farm level without dying.

If you don't make either of these then you can always just go back later it's fairly quickly

3. Do the remaining story levels
school sports level, city, army, etc.

It's a little tricky but you'll have to defeat all story mode bosses. It might be a little difficult but if you've already done the story mode it should be mostly trivial.

Just be aware the tank might one-shot you if you are low on health, so listen for the sound ques on when it shoots.

After you've beaten the tank
Continue playing until you get 100.000 in score.

Achievements

• Not Too Shabby - Score 50,000 points.
  
• UFO Wizard - Score 100,000 points.
  
• Score Surfer Dude - Complete all Score Attack waves.

It might be easier to do the score achievements by grinding an early level on story mode. But I did it in score attack

Good luck to the few souls who tries to venture into this game like I.