i lunged backwards, snarling.

Darius pressed his advantage, swinging again.
(My Internet was refusing to behave...)

(gotcha)

it snarled and ba ckdx up before taking flight.

Darius pulled back, and threw his axe, cleaving through the wing membrane and leaving one side nearly unusable.

it cried out in massove paijn and landed, staring up weakly. it rose, whimpering.

(whelp this complicates thins.)

(Negating every advantage possible. The wing is there, just the membrane is slashed. It can be repaired.)
Darius walked up and stepped on its neck, right at the base of it's skull with a small knife in hand.

(ah. but still. then again, this might be a Hiccup and Toothless situation from the first movie.)

it looked up, breating heavily and obviously terrified.

(Yes, but Hiccup wanted to help Toothless. Darius feels far less charitable, and they were in open combat just moments before. )
Darius grabs the dragon's undamaged wing and slashes that as well, screaming at the dragon about his ship and his crew and a myriad f obscenities as only a sailor can, finishing by asking it how it likes the idea of never flying again.

(eh. then again, the gang freed a dragon that was a gladiator and was almozt killed by Toothless in one of the side series episodes. so, its happened before.

also, i picked this sppecies for the main purpose of it being Dariuss dragon later. so, it kiiiiiindaaaa needs to live.)

it roared in pain, eyes wide.

(It will, assuming it can hunt on foot.)
Darius put the knife away, and took his foot off its neck,before delivering a vicious kick to its ribs.