I am little late like normal, but let's be real Aloalan Marowak has potential to beat most (if not all) the ultra beast due to his typing and ability. Game freak's way to balance these monsters was limiting the move pool meaning a very low lack of coverage, they are easy to predict, and while the Ultras can run some sets to boost their stats toy unreal levels, they just don't have coverage to beat their checks which forces switches and thus lose of stat boosts. There is is just low coverage, you need to bank on getting K.Os to continue a sweep, that can skyrocket your stats. On paper they are ridiculous, but in practice they can be beat, pretty easily. Toxipexs tho.....
Also
The set I built is pretty troll, it might standard, I wouldn't know cause I haven't been watching competitive battling, just laddering on Smogon and fighting people in game with Alolan Marowak.
-Flare Blitz
-Earthquake
-Shadow bone
-Will-o-Wisp (Mainly for utility, but it allows you to take on bulk-up Buzzswole)
Like I said, late to the party here sorry if this feels like a spam post, but honestly I don't see the Ultra beast getting banned to ubers. All it takes is just one god tier mother to beat them, Lusamine take notes on this proud mom!