Nihelego - Rock/Poison - 109/53/47/127/131/103
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: Clear Smog, Toxic Spikes, Power Gem, Stealth Rock, Psyshock, Thunderbolt, Sludge Wave, Psychic, Dazzling Gleam
Thoughts: Decent hazard setter that suffers from low Defense and shoddy typing. No room for both hazards, and lack of recovery prevents it from staying around.
Buzzwole - Bug/Fighting - 107/139/139/53/53/79
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: Thunder Punch, Ice Punch, PuP, Leech Life (80 BP now), Taunt, Hammer Arm, Superpower, Focus Punch, Lunge (80 BP Physical Bug move that lowers target's attack), Earthquake, Rock Slide
Thoughts: Physical beast that lacks the Speed, movepool, and SDef to use it. No Megahorn or reliable Fighting STAB is a huge letdown. This is especially terrible for its viability since the next UB on this list exists:
Pheromosa - Bug/Fighting - 71/137/37/137/37/151
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: QUIVER DANCE, Low Kick, RAPID SPIN, Hi Jump Kick, Bug Buzz, Ice Beam, Taunt, Roost, Focus Blast, Poison Jab, U-Turn
Thoughts: Is it going to die to any hit? Yes. With a offensive spread like 137/137/151, this doesn't matter. It can bounce around with U-Turn at high speeds, Spin hazards, and pressure walls with decent dual STAB. Absoulutley insane how min-maxed this thing is. Reminds me of a cross between Genesect, Deo-A, and Mega Lopunny.
Xurkitree - Electric - 53/69/71/173/71/83
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: Signal Beam, Thunderbolt, Calm Mind, Energy Ball, Volt Switch, Dazzling Gleam, Tail Glow
Thoughts: Ridiculous SAtk is offset by lack of bulk, Speed, and movepool. Why even bother with this? Tail Glow sounds crazy though.
Celesteela - Steel/Flying - 97/101/103/107/101/61
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: Air Slash, Leech Seed, Giga Drain, Flash Cannon, Iron Head, Seed Bomb, Heavy Slam, Earthquake, Flamethrower, Fire Blast, Stone Edge, Explosion,
Thoughts: Good balance of every stat, minus Speed. Interesting movepool; it could use any hazard and a good form of recovery, but the inclusion of Giga Drain and Leech Seed is unique. The main concern here is that its too _average_ to be viable.
Kartana - Grass/Steel - 59/181/131/59/31/109
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: Sacred Sword, Night Slash, Leaf Blade, X-Scissor, Psycho Cut, Brick Break, Swords Dance
Thoughts: Everything at first looks promising. It has an insane Atk stat backed by one of the best Speed in the game. Defensively, its typing and physical bulk give it good opportunities to switch in. The main issue here is that its movepool is lacking. Nothing I've listed has above 90 base power. It doesn't even have a single Steel-type STAB. Unlike Xurkitree it actually has some tools to do damage with.
Guzzlord - Dark/Dragon - 223/101/53/97/53/43
Ability: Beast Boost - raises most proficient stat every KO
Interesting Moves: Dragon Tail, Iron Tail, Crunch, Hammer Arm, Dragon Claw, Earthquake, Heavy Slam (1957.7), Flamethrower, Sludge Bomb, Fire Blast, Stone Edge, Dark Pulse, Draco Meteor
Thoughts: Definition of a tank. Access to insane bulk, decent offenses, and a varied movepool makes this thing look good. Its typing does leave it with some undesirable weaknesses.
Necrozma - Psychic - 97/107/101/127/89/79
Ability: Prism Armor - reduces power of SE moves
Interesting Moves: Moonlight, Charge Beam, Power Gem, Stealth Rock, Psyshock, Calm Mind, Psychic
Thoughts: No idea how this thing is supposed to fill out a moveset.