# will bring on them their own iniquity

Possible meanings are 1) "will do to them the evil things they have done to others" or 2) "will punish them for all the evil things he has done to others."

# cut them off

"kill them." 

# in their own wickedness

Possible meanings are 1) "while they are doing wicked things" or 2) "because they have done wicked things."