Ashe: Hunh!? What do you know about me!?
Master Albert: I know everything about you! As if you were my own daughter. I want you to grow! Evolve! Show me your strength!
So you have a pair of Arch-Enemies: a hero and a villain. And then... The villain gets interested in the hero.
The hero and villain are very similar to each other, and both grow aware of that fact. But they have different reactions. While the villain genuinely wants to take the hero under their wing, the hero is opposed to any friendly interaction — but may fear the villain has a point. The kind of obsessive behavior and mind games this generates on both ends is a prime source of Foe Romance Subtext.
If the hero and the enemy do end up becoming mentor and student, the ensuing relationship can range from the worst kind of Training from Hell to a downright parental role. Both will still probably end up at odds. And it'll end badly for at least one of them.
The Hero will usually consider The Mentor to be their Arch-Enemy and be very personally devoted to taking them down; The Mentor character is typically more amused by this than anything, and may take the role of a Stealth Evil Mentor. The presence of this trope may lead to a Mind Game Ship, a Teacher/Student Romance, or both.
Related to We Can Rule Together, but rather than offering a position, offers a study period. Note that this requires a mentoring role—Worthy Opponent offering a team-up doesn't cut it.
- Ra's al Ghul to Batman. He sees Bats as a mirror, and was once interested in him being the successor of his organization, The Demon.
- In Birds of Prey Lady Shiva takes an interest in training Black Canary.
- Shiva also took an interest in Cassandra Cain. Not because the teenager was her long-lost daughter but because she was one of the few on the planet who had a real chance of killing her in a fair fight.
- She also eventually feels this way about Huntress after the latter takes Canary's place during a battle to the death in order to save her friend, and gives Huntress the honorary name "Iron Owl" due to her refusal to go down without a fight despite being completely outclassed by Shiva in terms of skill.
- In fact, Lady Shiva is said to have a standing offer to anyone to train them, hero or villain. The price is that anyone who accepts, will have to face her in a Duel to the Death one year after they leave her tutelage.
- Ghostbusters (IDW Comics) has an arc that establishes Gozer's sister, the god of chaos Tiamat, as taking an interest in forcing a confrontation with the ghostbusters because the ants she once tortured for amusement now have the means to wreak merry havoc with the fabric of the universe.
- In the Green Lantern comics, Sinestro has taken an interest in Soranik Natu, the current Lantern from his home planet of Korugar. Where Sinestro was hated for being a Knight Templar tyrant (and the next Korugarian Lantern, Katma Tui, was hated by proxy), Korugar is coming to love Soranik. Both are viewing the peoples' growing devotion to her as practically asking her to be a dictator herself, which Sinestro views as her bringing order where he can't anymore while Soranik is greatly troubled by it. And it's no help at all that Sinestro is Soranik's biological father.
- Judge Dredd: The main character of the "Fall of Deadworld" storyline, Judge Fairfax, was once an acolyte of Judge Death, who still wants to recruit him as one of his lieutenants after they had a falling out. Fairfax just wants to ride out the apocalypse.
- In the Ultimate Spider-Man line, the second Spider-Man, Miles Morales, is approached by his uncle, the super thief Prowler, for training. Little does he know, the Prowler needs Spider-Man to deal with the extremely powerful Maximus Gargan—the Scorpion.
- Some tellings of Spider-Man give him this sort of connection to Norman Osborn, aka the Green Goblin. Especially when the Green Goblin's son is not living up to his father's expectations.
- Teenage Mutant Ninja Turtles: Like Ra's Al Ghul to Batman, the IDW version of the Shredder has decreed that only Leonardo is fit to inherit leadership of the Foot Clan.
- X-Men: Emma Frost offered her mentorship to Kitty Pride. Kitty didn't want to even think about it, and Emma was sincerely suprised why anyone wouldn't want to be like her. Emma and Kitty would develop a relationship over the years that included murdering and resurrecting each other.
- The Batman vs. Dracula: Initially, Dracula is quite intrigued by Batman, due to their similar motifs. He even offers Batman a prominent seat at his table. After Batman rejects the offer, though, Dracula vows to kill him.
- Treasure Planet does this, especially when it's becoming apparent Silver was Evil All Along. Subverted past the climax, however, when Silver slips into a somewhat benevolent role and loses his edge.
- Star Wars:
- Luke Skywalker and Darth Vader have strong elements of this, minus the Foe Romance Subtext because, well, squick. The fixation leads to both Last-Second Chance and We Can Rule Together moments. Of course, from Vader's perspective, he is neither villainous nor beginning an interest.
- Also the Emperor toward Luke, believing (rightly) that he is stronger than his father.
- Palpatine has it to Anakin in the prequels too. He became something of a father figure to the young Anakin in the hopes that he might one day corrupt him to the Dark Side, though he didn't go full-on until he realized how much more powerful Anakin had become than his previous apprentice, Count Dooku.
- Kylo Ren in The Force Awakens offers to teach Rey in the ways of the Force (in the middle of a duel, no less!).
- Watanabe of Unbroken is fixated on Zamperini. He even tells him that from the moment they met, he knew they were alike and that they could have been friends if not for their opposing sides. Zamperini mainly just seems creeped out by the attention.
- In the Alex Rider series, the Big Bad of the third book Alexei Sarov takes an interest in Alex. He takes him hostage and tries to convince Alex to accept him as his new father due to Alex's similarity to Sarov's dead son.
- In the Nevermoor series, Ezra Squall's primary motivation in most of his interactions with Morrigan is to convince her to let him become her Evil Mentor, insisting that he is the only one who can truly teach her how to master Wunder (which is actually true—not least because he murdered every other Wundersmith) and that he sees himself in her. He alternates between praising her abilities and strength, telling her she's better than everyone else at Wunsoc... and screaming abuse at her and reacting with anger whenever her good nature wins out over self-preservation. Why, exactly, he chose to spare Morrigan out of dozens of children who had Wundersmith abilities, letting her live and deciding she was going to be his heir, is a mystery.
- In The War of the Ancients, it's implied that Broxigar's prowess during his final stand against the Burning Legion, during which he managed to lightly wound Sargeras himself is one of the reasons the Burning Legion tried to recruit the Orcs.
- Curse of Strahd: Whenever newcomers enter Barovia, Strahd von Zarovich takes an interest in them in order to determine whether any of them is worthy to be his successor. However, he eventually decides that none of them are worthy as a successor, but he doesn't arrive at this conclusion immediately.
- Hazbin Hotel: After Charlie's pitch on the news for the Happy Hotel bombs miserably, Alastor offers to help the hotel not because he believes it will succeed, but so he can get his kicks from seeing the patrons repeatedly try and fail to redeem themselves. This, coupled with the fact that Alastor is the most powerful and most dangerous demon in Hell, naturally makes Charlie suspicious of him, but she accepts his support anyway considering he's the only denizen of Hell willing to help.
- In Volume 2, Cinder takes a very strong interest in Pyrrha Nikos after learning about her abilities, and has her put on "the list."
- In Volume 4, Salem orders Tyrian to capture Ruby Rose alive. It's unclear why she wants Ruby, but it's mentioned that her followers have "dealt" with people with Silver Eyes in the past.
- When he catches up to Team RNJR, Tyrian briefly mentions that, aside from Ruby, there's something about Jaune Arc, but doesn't elaborate.
- In Drowtales, Snadhya'rune Vel'Sharen sets her sights on Ariel Val'Sarghress due to the latter's bloodline, which contains a potent Anti-Magic ability and Ariel's own unique sorcery. The first inklings of it appear all the way back in the third chapter, but it's not until chapter 47 that the two meet face to face and immediately attempts to earn Ariel's favor. It ultimately fails because Kalki attacks Ariel, and Snadhya is so incensed by this that she later murders Kalki in cold blood for disrupting her and outliving her usefulness. Previously this method had worked flawlessly when Snadhya recruited her other "proteges" or students who showed unique abilities, including Mel'arnach Val'Sarghress, Ariel's sister (actually her mother).
- Sinfest: In what some may consider a cruel twist of fate, the Devil only begins taking an interest in Lil'E after the little devilkin gets his memory wiped and his personality reset to a more milquetoast one. This precedes the reveal that "Lily" is actually the Devil's biological son, ultimately resulting in Lily being moved into the Devil's Big Fancy House presumably for training as his heir. Of course whether or not Satan is the actual Big Bad of the strip or a Designated Villain is open to interpretation.