Man, this topic gets me pumped because I feel like I've been digging for gold in a very specific mine for years. The classic isekai scene is, let's be real, overrun with dudes getting truck-kun'd and becoming OP heroes. But when you get a female-led one done right, it hits different.
Some of the absolute standouts for me have to be 'Ascendance of a Bookworm'. Myne's drive isn't about raw power; it's this obsessive, world-changing passion for books that reshapes her entire medieval-esque society. It's a brilliant subversion—the 'cheat' is her modern knowledge, but the real strength is her stubborn, often self-destructive, perseverance. The world-building is ridiculously detailed, and watching her claw her way from a sickly commoner child to, well, you'll see, is incredibly rewarding.
On a totally different vibe, 'So I'm a Spider, So What?' is a masterclass in voice and survival. Reincarnated as a literal dungeon spider in a chaotic class-wide isekai event, Kumoko's manic, internal monologue is half the fun. Her strength is pure, gritty, exponential growth against impossible odds, and the way the narrative slowly pieces together the larger world and her classmates' parallel stories is superbly done. It's frantic, funny, and surprisingly deep.
Then you've got the political and tactical genius of 'The Saga of Tanya the Evil'. Tanya is a ruthless, hyper-logical salaryman reborn as a little girl in a magical World War I analogue. Her 'strength' is a cold, calculating intellect and a brutal dedication to efficiency as she tries to game the system to secure a safe, rear-line post, only to inadvertently become a legendary military asset. It's a fascinating, amoral take on the genre.
For something more recent and romantically charged, 'The Most Heretical Last Boss Queen: From Villainess to Savior' is a fantastic 'otome game isekai' where the protagonist, Pride, is reborn as the doomed villainess. Instead of just avoiding flags, she uses her foreknowledge and a formidable will to radically alter the story's course, aiming to save the kingdom and her own family. Her strength is political, emotional, and deeply strategic.