I beat him with a hardcore mobility and missiles build, but I’ve heard he’s much more doable if you switch to a superheavy build of all plasma weapons (the “Meefcake” is its name in the meta). One thing I noticed is his movement habits make him pretty vulnerable to missiles, which catch up to him when he holds still.
With mouse and keyboard where you can track him well he’s very fun to fight in close range since he likes to hold still for his missile volleys (you can pour in the damage while dodging), except that his ability to punish you with the bazooka means every screw-up is lethal when you’re in close. And that’s 10X worse when he gets his flaming sword.