6.2.2 Mr. Sinister

I am at 6.2.2 sinister, couldn't beat this guy with 5* r5 Nimrod, after 372 hits and 248 hits, he is still at 54* health.
My team is 6* Doom, 5* Dman, 6* Ultron, 5* Nimrod, 5* Kingpin.
What am I missing here?
Please help
My team is 6* Doom, 5* Dman, 6* Ultron, 5* Nimrod, 5* Kingpin.
What am I missing here?
Please help
1
Comments
OR is pretty easy boss. Many many possible counters.