Here is the full list of all 36 Garshasp: The Monster Slayer achievements.
Kill Hitasp without getting hit
Finish the game in hard mode
Execute 100 rage attacks
Execute 100 counter attacks
Finish the game in easy mode
Finish the game without saving
Finish the game without using any health fountains
Throw ten enemies in the water of the lake while on the raft. (with a splash!)
Kill Viamboor without getting hit
Finish the game in normal mode
Finish the game with no game overs
Kill Hitasp
Hit 7 enemies with a rage attack
Find the sixteenth Hoom seed
Do not get hit while sliding down in Ooshidaran
Fully upgrade the mace
Fully upgrade the sword and the mace
Upgrade the mace
Achieve the dragon mace
Kill Gandarava, the Sea Monster
Kill Gandarava without getting hit
Fully upgrade the sword
Do not get hit while sliding down in Jungle
Kill Khishma
Kill both Viamboors
Kill both Viamboor without getting hit
Kill 300 Enemies
Execute the first rage attack
Do not get hit while sliding down in Siavoshgard
Find the fourth Hoom seed
Slay Akatash
Upgrade the sword
Kill 100 Enemies
Find the first Hoom seed
Kill Viamboor
Execute the first counter attack