Broadly speaking, there are two kinds of antisemitism: gentile antisemitism and Jewish antisemitism.
The first type is the more common type that most people refer to when discussing this issue. It often, but far from always, involves violence or worse. More often it involves verbal violence without physical violence. And even more frequently is a simple old-fashioned hatred of Jews, simply because of jealousy or just because they’re Jewish.
Eisav Sonah L’Yaakov.
The second type, and what many of us Yidden run into more often than the first (simply because of our disengagement with Goyim as much as possible), is Jewish antisemitism. Some of these people even wear a Yarmulka and call themselves Orthodox. It can broadly be defined as hating those frummer (for lack of a better term) than oneself. Also out of jealousy, though they’ll never admit that reason and will attribute their hatred to a variety of other pretexts.
It’ll often play out in these Jewish antisemites denying the hated Yidden various benefits, privileges or rights. As well as deriding them amongst themselves and, even more prominently, to the outside/greater world. They’ll often derogatorily refer to them as “ultra” or “sects”.
This is found within Orthodoxy as well as outside of Orthodoxy, where very commonly non-Orthodox Jews engage in such behavior towards the Orthodox. Ironically, the left-wing in the Orthodox often try to convince these non-Orthodox Jews that they aren’t so ultra, and as such should be considered good, modern, with it, Americanized Jews just as the non-Orthodox. And will denigrate the hated “Ultras” in order to ingratiate themselves to these other Jewish antisemites.