If you want to break the game have two players roll Carcharadon librarians. One uses depths and the other uses maw. Kill everything within the maw radius.
I'm switching to a Minotaur assault marine Champion, so I'll be able to comment on that in future.
In another campaign, I'm playing a Guardian of the Covenant tactical Killmarine and I have to say Infused Knowledge starting off with a decent intelligence is very handy.
Pericula in mora
Danger in delay