Here is the tutorial of Hardest waves of Operation Undead Swarm. This is the one of hardest event ever in war commander, so you could follow these strategies and easily complete the event as you wish with minimum damage.
War Commander Operation Undead Swarm Waves 21
War Commander Operation Undead Swarm Wave 31 39
War Commander Operation Undead Swarm Wave 40
War Commander Operation Undead Swarm Wave 45
War Commander Operation Undead Swarm Wave 47
War Commander Operation Undead Swarm Wave 50
War Commander Operation Undead Swarm Wave 55
War Commander Operation Undead Swarm Wave 57
War Commander Operation Undead Swarm Wave 60