The first time you see Mike (Vlad's friend), he will be useful. Much later, you will have to fight him. To avoid fighting against Mike, let him take care of every mobster in Ragnarok. He should get killed. If this does not happen, after the last Mob fight, kill him just after the intermission sequence that presents the names of Vlad and Vincent. You should be able to take care of three to four enemies without his help.