The "Explosive Path" ability is unlocked by opening Gear Boxes in the Character Setup.
In the Escalation map Obsidian you will find a spot that the melee transformers can't reach. When you're on that platform, up to 7 will line up in front of you and stand still. They will throw stun grenades at you and some of the other transformers will shoot you from the distance, but they give you more than enough time.
I think you can do this 2 times until the melee guys are mostly gone.