Q:A couple thoughts about that last question... Undying only works if the Gravetiller didn't already have counters on it, and also say it didn't have any counters, and Undying triggers properly, could it possibly come back with 5 counters? 1 from Undying, and 4 from Morbid?
Whoops, I meant 5 counters. I’ll go back and correct that.
702.91a Undying is a triggered ability. “Undying” means “When this permanent is put into a graveyard from the battlefield, if it had no +1/+1 counters on it, return it to the battlefield under its owner’s control with a +1/+1 counter on it.”
It didn’t die with +1/+1 counters on it. Therefore Undying can still trigger from the graveyard and gives an additional +1/+1 counter on top of the Morbid ability the Wurm had.