You should never ever charge a map with a boss. after all units dont spawn endlessly so it’s a good idea to play slow and allow units to come to you, you kill them with little damage taken, and you continue. If you take a good amount of damage, just move back and resupply at base. Thats what i did when i beat Hedgegrow rigged, lost all my units, and did a hit and run back to base for 80 turns with only cw and supply.