Koko's hands were bloody well before Amyla.
All his life he had been a soldier– he had his first kill at just 6 years old. For the longest time, death was as commonplace as breathing.
For some reason, he thought it would be possible to run from his past, to find some pure water and wash his hands. The problem was that there was no such thing as pure water.
There was one simple word the entire world floated around: power. Even if someone claimed their actions were for love or to protect people or whatever bullshit chivalry they come up with, all of their actions ultimately boil down to one desire: power.
Even if an individual didn't want power it made no difference.
Amyla never wanted power. In fact, he'd say she hated her ability. He was the one who taught her how to use her power more efficiently, and she only practiced to appease him.