HC + a bit of analysis:
Dark is always seeking validation in anyway possible.
His literally only purpose was to kill chosen and he couldn't do that.
He was also the first stick that was semi liked by Alan. Alan, presumably, had no plans to torture Dark, he was just supposed to kill Chosen.
Dark was also left alone to fight.
Also since Chosen stopped wanting to do the attacks, Dark found it less fun too, but he thought he was the problem.
Dark wanted to be congratulated on his destruction. He was made for destruction, so when Chosen no longer wanted to do that, he assumed he wasn't doing it good enough.
Dark became more destructive. He killed more and more, Chosen hated it more and more.
Also when Dark showed Chosen his Vira bots Chosen wasn't like "Wow, this is so cool i can't believe you built this. Good job"
He got a blank stare/disapproval.
Dark made the vira bots to impress Chosen, otherwise why would he show Chosen. Even if he was going to do it anyways, he obviously wanted to show Chosen.
Dark cared about what chosen thought.
Chosen hated it.
That must have hurt.
Other then Chosen he wanted to be recognized for his destruction. He wanted to be credited for his destruction.
He wasn't.
The "Angel Of Death" was. That was Chosen.
Not him.
Also during the fight Chosen teamed up with Alan.
Dark was made to help Alan, and Alan was teaming up with the very stick Dark was supposed to destroy.
Instead of sitting out like he did last time, Alan chose to help Chosen.
Not Dark.
Dark would have thought that Alan hated Chosen, but no. He didnt.
Alan attacked Dark.
My poor boy :(