Instead of me repeating myself I'll just write some here so I can just copy and paste this to people.
This is just my opinions but at the same time people who loves a certain franchise will have the same idea but just shakes their heads and facepalm themselves to see some really bull crap ocs that just should die because they make no sense in that fandom.
These points are in no particular order.
Does your oc needs to be related to a canon character?
This goes for ocXcanon pairing either.
It is ideal that the least relationships your oc has to any canon character even the less remembered ones the better your oc will look.
To be honest at lot of people who have saw your oc being paired or related to a canon character just believes your oc is an attention seeker.
Unless you can generally make a good reason (which to be fair is near impossible to have a good reason besides having your oc background look better because you got a better backstage support from a well establish character) so word of advice don't do it.
Never distort canon characters.
This mean don't change them.
Most the time a canon character is change so much people think "who the hell is this?" just so happens people do something that causes the canon character to be changed for the worst.
Happens when people try to pair the canon character to a oc or making the oc related to them.
If you really like certain characters designs from a series but you don't want to distort the original make a fan version of that oc yourself.
If you like a canon character, you also can get inspired by said character and make a character based on him/her while still being careful not to make him/her a ripoff of the character they're inspired from. (suggestion from Skype Friend)
Research your fandom.
Don't pull crap that doesn't fit into a franchise/series you are making an oc for.
If your oc fandom is a heavy science-fiction type of setting don't put fantasy crap into it.
Vice-versa with a series that's hi in magic but low in technology.
If the universe your oc is trying to fit in don't expect your Oc should be able to do something that no one in that universe has done before example a series that doesn't play with genetic modifications don't expect you should make an oc with genetic modifications.
Or your oc is in a science fiction universe and your oc can use magic don't do that.
Crossbreeding with awkward races sometimes people do that but it doesn't make sense anyway it's fun making an oc that breaks the rules but it's not a good oc unless there were former examples in the universe.
Crossover ideas with other series. Example Super robots into real robots series. This is only applied for your Oc being a true fandom Oc if you are planning a crossover idea like in some games it works differently.
Learn when your oc is too OP.
Sometimes happens when your oc has god like powers either as:
God of Life can heal everyone, bring a person, people, a city, a country, the whole planet, the whole universe, the whole franchise back to life. Just don't if there's no god healer in the series already don't expect your oc can take that position.
God of Destruction, self explanatory aka can destroy everything etc.
Sometimes God of Life and Death aka can do both depending on the God's will.
Yeah don't do that no one likes a shitty over powered oc that doesn't fit the franchise.
God of time or in general time travelling abilities.
This sounds fun at first but OCs that can travel in time I generally despise.
It can be forgiven if they can't interact with the past but most people seems to do it that they are going back to the past to fix everything.
It's a common plot line for people to use time travelling so they can save the future but I just generally think it's a bad thing.
I also don't think time travelling is such an easy ability to use and it should be a very tiresome skill.
Same with time base ability it's a very powerful ability so the weakness needs to be equally as powerful do not use the stupid fatigue card.
Too much abilities.
You can have really strong ocs everyone wants their favourite ocs to be strong and the minors ones to take the sidekick roles but this goes to researching. Check some of the characters in that franchise and what they have that makes them strong and imagine what your oc could have that makes them just as strong as that character (if you are using the strongest character for reference just make sure your oc is just as strong and not stronger maybe a bit weaker and you be doing fine).
Too much unique abilities.
Some franchise have individuals with unique abilities and people wants their characters to do the same.
It's fine but you should check if the two abilities are mutually exclusive.
Try to limit your oc to have the same limitations to certain special abilities don't stack them all on them your oc is just attention seeking.
Having abilities that just doesn't fit anywhere in the fandom universe.
Example magic in science fiction.
A oc who is more or less a ripoff from a canon in the universe.
Extreme cases of wannabe is your oc taking over that canon's role.
This does not apply if you are playing a game that your oc is the canon's role aka the Player Protagonist.
When you describe your oc in one way but it does something completely in the opposite direction.
Example your oc hates violence and bullies but he will beat the daylights out of a bully.
Sometimes this happens due to the lack of explanations for your ocs if you need a contradiction in your character, thorough details/explanations are required.
Lack of explanations.
You are not explaining enough for your oc to let people be able to relate to.
My oc is a boy.
My oc is a 20 year old male.
My oc is a 20 year old asian male.
My oc is a 20 year old asian male. He has dark brown eyes but he has dyed his hair from black to hazel brown. He has an older sister and is currently away from his parents living with his relatives in a different area as it is easier to get to college than his own home.
The more little bits and bobs you explain about your oc the more the readers can relate to and it helps you to establish your character.
If you hate people bashing your ocs because they are very badly made bullshit wannabe that is overpowered and doesn't fit the genre of a universe/series/fandom etc.
Make your own universe.
This is what I done so if my ocs are powerful they can be but only in my universe.
I may add more if I can think of more stuff or be bothered with it.
Viewers can comment on here on their experience on making ocs.
I may not included stuff like drawing talent as not everyone is artistic.