Early game · first 8 minutes
Knock Rat King up with Kinetic Pulse when your lane partner can shoot him. Stand away from your lane partner between attacks so Scrap Grenade cannot hit both of you.
Dynamo vs Rat King
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Mid game · Walkers
Use Quantum Entanglement to carry a nearby teammate out of Scrap Grenade’s blasts or away as Rat King starts to slam his banner down. Heal with Rejuvenating Aurora from cover after you reappear.
Late game · Patron
Start Singularity when your team can shoot the enemies gathered around the banner. Catch Rat King in it as well, or wait until he slams his banner down so he cannot interrupt you with it.