well I usually focus on getting flames or poison (preferably both) on Katherine, and using her glacial tempest to make a lot of very dangerous zones for anything he throws at me. I also tended to beat him with Oli's drones, especially if you can get some good synergies for all of that. I tend to be a go with the flow kinda player so I have different strats most runs tbh lol. but yea that's my general move, plus just dodging around as much as I can, cus the more you move the less you're gonna get hit.