Kommo-o has a lot of great tools at his disposal, such as Dragon Dance, Autotomize, Swords Dance, etc, but he's missing a lot of good things that should make him a good enough threat. He's lacking a lot of nice and powerful Fighting STABS, with his most powerful being Focus Blast, though that is somewhat unreliable due to it possibly missing... a lot, and his second most powerful being Sky Uppercut, which has decent power, but has a bit of an accuracy issue, though not as bad as Focus Blast, and doesn't pack as much of a punch as Close Combat. He has nice mixed stats, as well as access to Flash Cannon (which can be used as an alternative or with Poison Jab for Fairies, who would otherwise wreck Kommo-o up), alongside a lot of other options that give Kommo-o decent coverage and power. His bulk is also fairly solid at 75/125/105, so it looks like Kommo-o can take a couple good neutral or resisted hits before he calls it quits.
110/100 offenses are quite workable, though you won't punch many holes in a team without some EV investment and/or boosts, so do mind that. Clanging Scales is quite the move. -20 less power than Draco Meteor, but doesn't result in a power drop makes it quite a spammable move. The loss of defense is quite worrying at times because of the fact that you are easily revenge killed after a use or two, but because you don't lose power with each use, it can be fairly negligible under the right conditions.
85 speed is quite decent for this Gen. Lots of Pokes are slow this time around, and Kommo-o does have access to speed-boosting moves, so 85 speed is decent.
Anyways, I think Kommo-o has potential to be a good enough threat, but it's missing some good moves. The stat spread is quite good enough for what it's worth, so Kommo-o could do with going physical, special, or mixed, and taking hits won't be too much of a problem, except when Fairies are around, but maybe a Roseli Berry can mitigate it. Maybe give it some Fighting STABs like Close Combat and/or Cross Chop, or maybe Drain Punch for utility and longevity. Mach Punch could be useful for priority. More coverage moves like Gunk Shot, Meteor Mash, Bullet Punch, the Elemental Punches (come on, now!), and maybe some other lil' additions like Aura Sphere, Calm Mind, and Knock Off.
Okay, that's good enough. Might be pushing it, though...