Risk of Rain 2 and Robo Quest are probably up your ally because you like Ultra kill

But if you want to diversify genre, here are some that I would recommend

• Card Games - Slay the Spire (Its like a card game and rogue like combined)
• Rogue Like - Hades is currently one of the top tiers in rogue like dungeon crawler
• RPG - Baldurs Gate 3, even if you end up finishing the game, how you ended up finishing it is what makes it so replayable. Each character has their own stories for you to uncover. Larian’s other gem is Divinity Original Sin 2 too
• Sandbox Games - Minecraft of Terraria
• Arcade - Most arcade games are highly replayable because thats their whole selling point. Currently I am back to playing Temptest 4000
• Hack n Slash - Grimdawn, nuff said

Yeah Shotgun king is nice and is also very moddable too