Precision Frame Grenade Launchers and wait for Power Bricks. They have the widest Blast Radius and most of their damage is weighted in the Blast Radius (which equals tagging more enemies with higher damage numbers that aren’t grouped up right on top each other). You just need to learn to time Remote Detonate right. You can get a Year 1 “Orthrus” from Nessus still if you haven’t played through Year 1. Year 2 Terrain Wind also has the Remote Detonation perk but it’s Blast Radius is a little smaller. If you played Year 1, then “Sunrise GL4” has best in-class stats. Iron Banner’s “The Day’s Fury” has Spike Grenades. If you don’t want to learn how to Remote Detonate, Adaptive Frames with High Explosive Ordinance Perk should distribute more damage to the Blast Radius but you need to either direct impact Guardians or aim for the Floor at their feet to do the consistent damage. Easier to use but a little more constraining.