Here is the full list of all 27 Lost Bros achievements.
Everyone survived the final sequence.
Kill the owl in the swamp.
You got the worst Lost Bros ending.
You beat Lost Bros!
You collected all 9 orbs!
You unlocked all 9 upgrades!
You defeated the boss of 1692 AD.
You defeated the boss of 2237 AD.
You collected all 3 masks.
You answered three Sphinx questions correctly.
You defeated the boss of 220 BC.
You defeated the boss of 10,000 BC.
You defeated the Minotaur, Medusa, and the Hydra in 735 BC.
You defeated the boss of 1742 AD.
You dug up fifteen things.
You defeated the boss of 1968 AD.
You unlocked the field jacket for gunman.
You purchased the sunglasses and cutoff shorts.
You spent your hard earned cash on the orb from 1864 AD.
You've died 1000 times.
Use the jukebox.
You died for your first time.
You got the mid Lost Bros ending. (Beat the game in under 10 hours)
You got the best ending! Awesome job! (Beat the game with under 200 deaths)
You beat the game on hard.
Wow..you beat impossible...here's a wheat muffin..