And here we come to what I think is the most misinterpreted boss on our list, the flamboyant Shadow Kanji himself. Persona 4 is my second-favorite video game of all time because its cast is so well realized. The fact that almost all of your bosses are their Shadows is a major contribution. It's one thing to have hints at your party members' deep fears and insecurities -- it's quite another to have them manifest in such a way as to beat your face in.
Oh, and if you haven't played Persona 4, what the hell are you doing with your life? Get it now. I think it's on PSN. It's good shit. I'll spoiler tag the below, just in case, though the first paragraph itself was a bit spoiler-y.
Yosuke's shadow manifests from his selfishness and frustration with a new rural-town life that bores him to tears. Yukiko's shadow manifests from her hatred at being powerless to make her own choices for her career and life (and incidentally why her social link is the worst in the game, don't @ me). What of Kanji's then?
Plebs on the internet: "Well it's because he's secretly gay, duh!" Me, an intellectual: "...Not necessarily."
Reread that intro dialogue again. What is the Shadow hung up about? It's not about how he actually loves men -- it's about how he despises women. But as with the other shadows, it's an exaggeration of a deeper insecurity: that Kanji, who enjoys cute fluffy things, sewing, and knitting, is too un-manly for a girl to take seriously. His status as a tough-guy delinquent is a front to overcompensate for it. Add his surprising attraction to Naoto, who he currently believes is a man, and you get someone so confused by his sexuality, gender roles, and desire to be desirable that it turns into a monster that figuratively beats you in the head with male sex symbols.
Then it literally beats you in the head with male sex symbols.
Could it be that he is gay (or at least bi, considering he still gets the doki-dokis for Naoto when he finds out her actual chromosome makeup)? Yeah. But despite what this shadow would have you believe, it's not a guarantee.
Okay, enough armchair psychoanalysis of vidya gaem characters. Let's talk about the fight. Most people think of Shadow Yukiko as P4's "wake-up call boss," but for me, it was one boss afterward. See, this is the first time you have to deal with a boss that has adds, and the Nice Guy and Tough Guy make a fairly simple boss much, much more tedious. In the video above they take down the Tough Guy first, but that's because it's in Very Hard where he hits like a truck. In normal mode, the Nice Guy is the larger problem, unbeknownst to dumbass me who thought "hit the guy that actually deals damage" was the right call.
P4 was my first Atlus JRPG, and Shadow Kanji in particular teaches you how to approach big fights in the Persona and SMT series. By this point you've learned the weakness system pretty well, but unlike most other JRPGs where temporary status buffs aren't worth the action economy lost, playing with your -kajas and, just as importantly, preventing the enemies' -kajas is crucial. Guess what Nice Guy does? If you guessed "puts -kajas and protective barriers on the other enemies," congratulations, you're smarter than I was. In Golden he even cures Dizzy from the Tough Guy to boot. Yeah, I got wrecked.
For story, Kanji is one of the most nuanced shadows, precisely because he screams to be the opposite. For gameplay, he teaches you to git gud for the trials to come. I was surprised he's so low on this list, but that just means even better entries are yet to come.