Alright, so there's actually a decent number of images which feature this character, so I'd like there to be a tag. But there's also an artist tag with the same name, so I'm not sure where to begin. How do I create a character tag without overriding the artist tag?

Adonis, the Mega Blaziken.

An image pool featuring him:
https://e621.net/pool/show/3513

Some more images with him:
1739984
1739985
1830399

You can use a _(character) suffix to differentiate between the two, so it would be like adonis_(character) or something along those lines.

Ratte said:
You can use a _(character) suffix to differentiate between the two, so it would be like adonis_(character) or something along those lines.

So, like character:adonis_(character) when adding the tag I guess?

There's also a Greninja character by the name of Zero, but zero_(character) is already taken.

dobiman said:
So, like character:adonis_(character) when adding the tag I guess?

There's also a Greninja character by the name of Zero, but zero_(character) is already taken.

Yeah, avoid _(character) if there's possibility for more than two things to have same name.

Best approaches are characters_full_name and character_(owner) formats as there's less disambiguity and incorrect tagging.

Also yes, either use character: prefix when first tagging or tag regularly, then change tag type from Tags page found in top panel.