Do you really, really dislike that one pony? You know, that one who does the thing you don't like? Maybe there's an artist whose style you just never want to see. Or perhaps you find anthro or humanized versions of the characters rather unpleasant? Well, what are you to do if people are uploading those pictures anyway? Never fear, the tag blacklist function is here!
You most likely already found the place where you edit your blacklist, but if you haven't, click "My Account" at the top left of the screen and then click "Settings." Scroll to the bottom of that page and you'll find your blacklist, most likely fresh and empty.
To use the blacklist, enter a tag that you never want to see. For example, suppose your least favorite pony is Twilight Sparkle and you never want to see pictures with her. Enter "twilight_sparkle" on its own line and pictures with her will be gone forever. Basically, it's like your very own inverse search that's always turned on.
You can enter multiple tags on one line, too. If, for another example, you are okay with Rainbow Dash but dislike the EqG version of her, you can enter "rainbow_dash equestria_girls" and you'll never see EqG pics with Rainbow Dash, but you will still see other EqG stuff and other pictures of the blue pony.