Faith also has some pretty good showings, but they're kind of interspersed around the show.
Glory seemed impressive though, bringing down a building with a stomp of her foot puts her into the MU brick categories, but she was substantially stronger than Buffy.
My understanding is that it was more consistent in the comic, but in general, she can break through brick walls easily, bend jail cell bars, shatter statues with her bare hands, lift a large I beam easily, and have sex forcefully enough to literally bring down a house.
Cap has a few feats at about the same level, and WAY more appearances in which to showcase his strength. Blue Beast is in the 2-5 ton range, and got OWNED by peak Human Cap in a fight during Infinity Crusade. I put Buffy in that Beast range, definitively stronger than Cap, but not necessarily by a lot. A good showing might have her as high as 4 or 5, with her top feats being similar to some of those by 70's TV Wonder Woman, but usually she seems closer to 1-2 ton range, but maybe some of that is motivation or whatever...there's always some inherent inconsistency in comics as well.
BUT, thats why I think its clear she's not as strong as 70's TV wonder woman...WW has a good feat about every episode that matches Buffy's best. TV Hulk did too, with a few that were substantially above even that, though hard to quantify. Steve Austin had similar level feats regularly, but is only about half bionic, half normal, so overall, Buffy might well be his superior, though that bionic arm might be able to pack more punch than she can...his non bionic isn't competitive.