Happened all the way back during the creation of the X-Men by Stan "The Man" Lee himself. When creating the original team of five, Lee decided he wanted to re-use the character of the Human Torch, but with ice powers instead of fire. The youngest member of the team, and also the most irresponsible and hot-headed, with the opposite superpower... say hello to Iceman!
Abigail Brand's half-brother Lothi in the S.W.O.R.D spin-off has major similarities of appearance and personality to Tank Girl's boyfriend Booga. Each character is a Lovable Rogue who isn't as cool as he tries to be and looks like a humanised kangaroo (which Booga actually is). About the only difference is that he's green.
The future Sentinels bear more than a passing resemblance to The Destroyer from Thor, with their height, metallic exterior, Nigh-Invulnerability, and faces that open up to reveal a Death Ray.
Their grey coloration, lack of facial features apart from monochromatic eyes and adaptability also evoke the version of Amazo from Justice League.
X-Men Origins: Wolverine: In the comics, adamantium is a man-made metal that was created in a laboratory. The movie instead establishes that adamantium comes from a meteorite that crashed in a small African nation, where the locals worship it as a sacred treasure. That's pretty much exactly like vibranium, the Wakandan metal from the Black Panther and Captain America comics.
Colonel Moss from Wolverine and the X-Men (2009) was heavily based on Ultimate John Wraith, right down to having the same mustache and a backstory involving Wolverine scarring his face.
