Here is the full list of all 40 I Hate Running Backwards achievements.
Finish a loop with all six curses active
Heal for 20 health during one session
Destroy 50 watchtowers
Use ultimate ability 5 times in the same run
Deflect 500 projectiles
Detonate 50 explosive traps
Kill Scrapjack using only the hammer
Kill the Scorpion King boss
Collect every powerup in one run
Kill the biomechanoid without being hit
Kill Scrapjack boss
Kill Biomechanoid boss
Destroy weapon crate
Die
Kill 1000 enemies with a hammer
Gather 5k chunks from destruction
Finish a game loop
Kill the werebull
Kill Ugh Zan without taking any damage
Finish a loop without receiving damage
Kill the Scorpion King before he burrows
Get the combo counter to x50
Knockback 100 enemies
Deflect 50 cannonballs
Kill 10 RoadBulls on the Road ground
Kill the Lava Golem boss
Destroy 30 mines while invulnerable
Gather 50k chunks from destruction
Kill the second form of Ugh Zhan boss
Get to the Scorpion king using only the hammer
Freeze 100 enemies
Kill Ugh Zan boss
Deflect 20 rockets
Unlock 15 special weapons
Destroy a secret trash container
Kill Biomechanoid while four curses are active
Destroy a special crystal in the Crystal cave
Kill Scorpion King while two curses are active
Collect 666 souls
Finish a loop without receiving damage with all six curses active