How do we call tag where is there group of people in general (i personally searching Fate series with as many characters as possible)?

See help:cheatsheet:

Tag counts
chartags:2
Search for posts with two character tags.

Range qualifiers
id:100.. or id:>=100
Search for posts with an ID number of 100 or greater.

Fate characters often have multiple tags per character present, so you might need to use a sufficiently large number.

Try something like fate_(series) chartags:20..

Aside from the chartags metatag, we have 6+boys, 6+girls and 6+others. There’s no tag that counts all characters present.

PS: Please choose a more descriptive topic next time. “How to search for groups of people” is more helpful than “question”.

Thank you!

You can also order the posts by the number of tagged characters, for example fate_(series) order:chartags. (That gives a bunch of crossovers, though, so you'd have to add -crossover but that goes over the 2 tag limit.)

Some other searches to try are fate_(series) everyone and fate_(series) absolutely_everyone.

Thanks you, fossilnix, everyone tag is just what i needed!