In Star Trek II: The Wrath of Khan, the eponymous villain, Khan Noonien Singh (Ricardo Montalbán), actually has a legitimate reason to hate iral James T. Kirk (William Shatner) and Starfleet. Of course, Khan's expression of his hatred was pure supervillainy, and he cemented his status as the greatest Star Trek antagonist in The Wrath of Khan. But while Khan is a man, his core issue with Kirk does have a degree of merit.
Introduced in the Star Trek: The Original Series season 1 episode, "Space Seed," Khan was a genetically-engineered 'superman' who was once the ruler of a quarter of the Earth's population. Khan and other Augments seized power in the late 20th century, sparking a conflict known as the Eugenics Wars. Once he was on the losing side, Khan and his followers fled Earth on the S.S. Botany Bay and spent the next 300 years in cryogenic sleep until they were awakened by Captain Kirk and the Starship Enterprise. Khan wasted no time in taking over the ship and trying to kill Kirk. Once Khan was defeated, Kirk left him and his people to settle on the planet Ceti Alpha V.
Khan Has A Legitimate Grievance Against Kirk & Starfleet
In Star Trek II, the USS Reliant beamed down to the hostile desert world of Ceti Alpha VI and found Khan and his followers. Captain Clark Tyrell (Paul Winfield) and Commander Pavel Chekov (Walter Koenig) were shocked to learn that they actually beamed down to Ceti Alpha V. As a furious Khan explained, Ceti Alpha VI exploded six months after Khan and his followers arrived at Ceti Alpha V. The planet's orbit shifted, turning the world into a barren wasteland that killed many of Khan's people, including his wife, Marla McGivers (Madlyn Rhue).
For those two decades that Khan and his band were struggling to survive on Ceti Alpha V, neither iral Kirk nor anyone from Starfleet ever bothered to check on them. As far as Khan was concerned, Kirk had left them there to die, and the Augment nursed his resentment of Kirk for the next 20 years. While this rationale doesn't excuse Khan's horrific acts of revenge, he has a point that Kirk never gave Khan a second thought after "Space Seed," and there was a marked degree of irresponsibility on Kirk and Starfleet's behalf to never follow up on Khan and his followers' progress on Ceti Alpha V.
Lower Decks Mocked Starfleet's Lack Of Follow Through
Star Trek: Lower Decks indirectly gave Khan a bit of his due when they also mocked Starfleet for being "bad at follow through." It seems to be a systemic problem within the organization that once Starfleet solves a planet's problem, they simply move on and don't follow up. Star Trek: Lower Decks' mission statement is actually an answer to this issue; the USS Cerritos and the California-class starships specialize in Second , which is that all-important follow-through Starfleet was sorely lacking. By the end of Star Trek: Lower Decks season 3, this mission was dubbed "Project Swing By."
Unfortunately for Khan and everyone he encountered in Star Trek II, Star Trek: Lower Decks' Second was instituted by Starfleet about a hundred years after The Wrath of Khan. The Augments stranded on Ceti Alpha V had just cause to hate Kirk for abandoning them. But it would have been better for everyone if Khan had taken his grievance up with the Federation Council instead of trying to murder Kirk and everyone from Starfleet who crossed his path in Star Trek II: The Wrath of Khan.