One Shot Abyss Cleaner

With the help of Symbiotes passive, life leech from secondary and armor coming from modules, perks and catalyzer, its very hard to kill this guy, something needs to one shot you

Always use your tertiary ability since its important for both tanking and killing
Ur's roar gives Damage Reduction meanwhile Sek's roar gives armor reduction (enemy will take increased damage even if they dont have armor)

How to one shot bosses: Switch to Sek, use tertiary on boss to apply armor reduction, switch to Ur and hold Primary, then hope for crit chance to occur
When you come to a point that you cant one shot them anymore, Just dont switch to Ur and slice them with Sek (at level 200, I was able to kill the bosses in less than 5 min)

Note: Be careful with the small lesion monster that duplicates when it dies. Sometimes they deal absurd amount of burst damage so just be ready to use your heal from T while killing them just in case, and the ancient vanguards
Edit 1: Ur-sek in last two pictures looks different because thats a different run and I decided change my colors and two of the modules, I wont edit the listed modules here because they are more guaranteed to survive than the one im using.
Edit 2: I died at 248 because of my own foolishness