Some superheroes are actually people who don’t have anyone from their families with them. But well these, they have no one even from their race, which makes these superheroes the last ones. Have a look:
Gamora is the last person of her species, the Zen Whoberis. She isn’t called the ‘deadliest female in the galaxy’ for no reason. A real fierce warrior, Gamora is a really skilled fighter. Well if her battle doesn’t give it just look at her death count, if that also isn’t enough for you, just know this that she was raised and trained by the mad Titan, Thanos himself.
J’onn J’ones is a really tragic character. Apparently the last surviving green martian who witnessed the death of not only his family but his entire kind. He is said to be the second most powerful member of the Justice League after Superman. He has Super strength, can fly, go intangible, can perform telekinesis, has regenerative abilities, has 9 senses, Martian vision, can manipulate mass etc.
Galactus or as he’s known, the devourer was not someone who always had a planet for his meal. He was once a hero, who tried to save his own universe but couldn’t. All died and he sucked up all the cosmic energy, after which he became Galactus.
Yeah, this is no surprise to anyone, the ‘Last Son Of Krypton’ came to Earth when his planet was destroyed. His parents put him in a pod which lands him onto Earth. Here he develops super senses and more powers such as flight, X-RAY vision, super strength, flight etc. He goes on to be arguably the best superhero in the DC universe.