How do players do insane boss damage

Hello everyone, I've been playing for quite awhile and the only thing I struggle with is end game boss/single target dps.

Recently got a great Dante build going where I can shred level 180 eximus and do steel path easy but going into the Belly of the Beast mission I barely did any damage to the sister. Same during the archon hunt, had no issues until the boss where my frame and weapons just tickled him.. I have other frame builds that are similar but all lack big boss damage.

I really do appreciate any tips and tricks! I am pretty endgame so currently own majority of weapons and frames in the game. I do use Overframe.gg on some builds but still feel like I'm severely lacking on boss damage. Any help is appreciated!!