Early game · first 8 minutes
Shoot until Afterburn ignites Rat King, then move behind cover while he burns. If Scrap Grenade lands beside you, move away before firing again.
Infernus vs Rat King
What's giving you trouble?
Full matchup plan
Mid game · Walkers
Use Flame Dash to leave a burning trail as you retreat toward cover. If Rat King follows, the fire damages him while you wait for Royal Pestments to end.
Late game · Patron
Activate Concussive Combustion before using Flame Dash to reach the enemies around the banner. Once Concussive Combustion starts, Rat King cannot cancel it by knocking you up.