Goblins IX: For that, you shall DIE!

[Morquard]

Good people can still have bad sides, just because they dont show it doesnt mean it doesn't exist. and he IS a goblin, a species that is naturally inclined towards evil i beleive.

Yes that's pretty much where I was going with this.

However I do know that the entire premise of the comic is that goblins and all the "monster races" aren't necessarily evil. The entire GAP is non-evil (Ears called out he's a LG paladin in one strip, he'd fall for associating with evil) for example.

However that does not mean the potential is not there. And most people have darker sides, they usually just keep them in check by reason and rationale.
At the beginning before Klik, Dies was too scared to do anything. That could actually mean that he had developed a very dark side in response to all that in his mind at least, he just never got to act on it. And when he got the hand his subconscious used that hand to strike out when he was threatened, using said darker side of him.

But that's all speculation.
It could just be that this is how those creations always end up. After all Klik said that this practice is strictly forbidden by his race under all circumstances. Maybe they had this problem with those evil clones before.