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