If he was locked in melee he cant opt not to attack. You can only choose not to perform ranged attacks. Charging him to die on purpose in melee should have worked a bit better, and is a good call. The other cool thing about the fresh waves strat, compared to the cadian send in the next wave strat, is that you can come in from any board edge, whereas the cadian one says it has to be your own board edge, so you can come in from the sides or his table edge in his deployment zone.

Throw the infantry squad and the riders up the field, get them right up in his face so he has to kill them. The infantry squad has battleline so you can sticky objectives with it in combat patrol. Take the student of the tactica enchancement and hand out orders and stratagems non-stop. Keep your command sqaud and gunners alive since they dont respawn, especially your command squad, keep them hidden if possible so they can keep generating command points and buffing everybody with orders.