Monster's you've Slain

[Zelrius 0]

Hell hounds

Nepents

Minotaurs

Scorpions

Tree Ents

Magma Lizards

Cerberus Guardians

Living Stone

Boars

Wolves

Bats

Wasps

Nargul

Yeti

(And there is more that I cannot Remember :\)

Bosses:

Amber (Fourth Floor)

Red Diamond Hunter (Event)

Cupid (Monthly)

Twinfire Phoenix (Monthly)

Bone Knight (Monthly) 

Frosty the Warlord (Monthly)

Cerberus (Quest)

Cerberus Again (before the quest was made, just for fun)

Wasp Queen (Quest)

Snow Beast (Essence of Steel)

Medusa (7th Floor Boss)

? (Forgot the Fifth Floor Boss's name =( )

Guardian (8th Floor Boss Fight)

Hydra (Ninth Floor Boss Fight)

Repentance (Quest)

Sand Shark (Quest)

Banshee (Quest)

(If I remember more monsters and Bosses, I will add them.) 

[Takao 0]

yeah that's cool and all, but has zel ever killed a cactus?

didn't think so.

checkmate.

[Kiru 0]

Boars

Bats

Nepents

Magma Slime (Zel this is the thing that caused you to disturb Kiru that one day ;-) 

Wolves 

Yeti 

Wasp 

Minotaur 

Ant things

Armored Knight

Kobold

Skeleton Knight things

Bosses:

Forgot the name (1st Floor boss) [Fought on other account but I'm too lazy to log onto that one and say this lol]

Forgot the name (2nd Floor boss) [Fought on other account but I'm too lazy to log onto that one and say this lol]

Cupid (Monthly)

Twinfire Phoenix (Monthly)

Bone Knight (Monthly) 

Hydra (9th Floor Boss)

Repentance (Quest)

Sand Sherk (Quest)

As for people I haven't slain anyone per say but I have injured a lot xD