Well he already has Meat Hook to drag the enemies close, Bloodlust to give him a nice DPS boost and this "TNT Bomb" skill, which i guess is somekind of nuke.
So he already has tons of damage. The last skill should some kind of melee disable skill. Slow, stun, snare etc. Anything that keeps the enemy from running away. Tho a channeling spell would be pretty bad, cause seems like your Hero relies so much on his autoattacks.
It's kinda hard to give you an exact spell since i don't even know what kind of map it is.