Something really important that I hadn't seen mentioned is that pocketed items disappear if they're not used within 30sec. Upon finding out pocketed tree is a OHKO I immediately started workshopping a double Villager team, but we noticed that by the time we got a tree setup, it wasn't they're anymore. So just be mindful, and make sure to pass the tree back and forth regularly to keep it in play, since repocketing resets the 30sec timer.
Note: this works in every case. With Diddy's banana, ROB's gyro, Bowser Jr's mechakoopa, etc, unpocketing the item, then immediately repocketing it resets the timer and still prevents them from spawning another.
Also, Villager team has a team true combo into the tree.
V1: grab/u throw
V2: footstool
V1: usmash
V2: pocket (drop tree)
V1: pocket (absorb tree)
It's relatively fast, and kills regardless of percent, plus it leaves the tree in play for another OHKO. The downside is that fast characters can interrupt it, but there's still the potential that they'll kill themselves with the tree by trying to interrupt.
And yes, it's inescapable. If your opponent is getting away from it, you're footstooling too low. It's easiest if V2 spams jump, that way 2nd jump comes out sooner and he starts falling earlier, and he'll footstool at the first possible instance.