*So far.
I can't call this all Kanto bosses when I'm visiting areas outside of Kanto and facing trainers from the Anime movies. Also there's a chance I may have missed a trainer or two so apologies if there is a fight that you had that doesn't pop up on here such as the Giovanni fight or the Team Valor Leader. I never bothered to catch Celebi to unlock that fight and I deleted my recording of the Candela fight by mistake.
I'm also NOT covering the Gym Leader Rematches here due to how the system to fight them works (they appear in Saffron Dojo at different times of the day of the week and you are given no hints of what time/day a Leader will appear outside of Blue so I just skipped fighting most of them as I found it annoying trying to spot all of them) and due to my team being 10+ Levels higher than their rosters by the time I got to them like you see with the Stat Trainers. I may make a separate video on them if I can scrounge up a backup team to take them on.
Pokemon Polished Crystal is a hack of Pokemon Crystal by Rangi. It's an improvement hack with extras much in the vein as Renegade Platinum and Red++ featuring many of the bells and whistles you'd expect from a modern Gen 2 hack (Abilities, Phys/Spec Split, Fairy Type and other later gen mechanics among others). Elements from HGSS are present in here with character sprites and some narrative segments lifted from those while original content/areas have been sprinkled throughout the game.
0:00 Professor Elm
5:38 Agent Looker (not technically a boss but hey, DPPt rep)
8:36 Leader Lt. Surge
13:23 Leader Sabrina
17:11 Leader Misty
23:01 ExElite Agatha
29:31 Leader Erika
37:08 ExElite Lorelei
42:22 Psychic Inver
51:14 Pokemon Trainer Flannery
57:00 Leader Janine
1:01:47 Leader Brock
1:06:05 Silver
1:10:00 Leader Blaine
1:13:39 Pokemon Trainer Buck
1:17:55 Pokemon Trainer Mira
1:21:34 Pokemon Trainer Blanche
1:25:03 Pokemon Trainer Spark
1:28:44 Pokemon Trainer Anabel (shouldn't this have the Hoenn battle theme like with Flannery?)
1:31:29 Collector Lawrence
1:37:45 Pokemon Trainer Cal
1:42:05 Leader Blue
1:46:48 Collector Lawrence 2
1:51:49 Final Lyra (Wally's theme GET!)
1:56:24 Final Silver
2:00:00 Professor Kukui (no Alola battle theme? Sadness.)
2:04:20 Elite 4 Will
2:08:07 Elite 4 Koga
2:13:24 Elite 4 Bruno
2:17:36 Elite 4 Karen
2:23:28 Champion Lance
2:29:28 Professor Oak
2:34:32 Pokemon Trainer Red
2:39:57 Pokemon Trainer Cheryl
2:42:26 Pokemon Trainer Mira 2
2:45:39 Pokemon Trainer Buck 2
2:48:17 Pokemon Trainer Anabel 2
2:51:17 FINAL BOSS: Pokemon Trainer Green