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