It does the same damage regardless of gear. It is massive damage, which is unavoidable 99,999 to target. Everyone else gets damage equal to 30% of their max health.
It works as an offensive gimmick in arena: If you use Palp's ability to drain health from probe, you can blow up someone right away and damage everyone else. Problem is, probe can't use the ability if at full health or if it's the only one left. So it's really easy to get around on defense.