If you've ever had an issue with numerous similar characters, heres a little tutorial that may help you.
Things people generally have serious issues with are
-Apperance
-Background
-Personality.
I'll work on these 3.

APPERANCE
If everyone in your story has the same haircut, or the same outfit, or the same anything, somethings wrong. Do something to the character to make them stand out. Scars are the easiest way out of this situation, but not the only way. Dont be afraid to disfigure them. Take off an arm and replace it with a gun, put them in a wheelchair or are they mechanical from the waist down?
Mabye half animal?
On to the hair and eyes. Mix and match colors. Different colored eyes are a favorite, and multicolored hair is difficult, but fantastic if you do it right. Go search some hairstyles. Dont stay safe with the usual medium cut, go clippy nightmare! Make there hair as wild as the characters themselves.

BACKGROUND
Everyone has a story. So all you characters should have one too.
I know that a fan favorite is “Orphan” or ‘parenless’ or ‘runaway’. Not saying those arent good Ideas, but people get tired of the same thing after a while. Do something different. And if you do want to keep the standard Ideas, then switch it up:
-Why did they run a way?
-Where are there parents/why did there parents die? (link it to the story)
But those have been used again and again as well….
Also, please, try not to reveal the past in the first chapter! Give hints to it along the way, and make the entire story come in when it is the most revelant (ex. a battle with his parents killer)

PERSONALITY
Dont characterize your character into types. No ‘silent type’ or ‘annoying’ or ‘tsundere’. Make a character all your own. heres what you should do:
Give them a face and inside personality
A face personality would be the one they show under normal conditions or to people they dont really know or care about. But the inside personality should be the one they show in only the worst or best of situations, and at that, only to people they really know, love, or trust. That makes for truly the event when the other personality is seen by the readers. But dont show this personality all the time. Then it will be another face personality. Make it a special moment when this happens.


And there you go. My somewhat short tutorial. I hope that now youll think more about your comic and it will be less standard!