。
You're really self-centered, you know that?
Literal
Truly self-centered [is-だ] [exclamatory-な].
自分勝手 is a な-adjective meaning 'selfish / self-willed,' literally 'self's own way.' The sentence-final な is the plain-form exclamatory particle expressing the speaker's own reaction or mild complaint — distinct from ね, which seeks agreement from the listener. な is introspective or monologic, often masculine-leaning in casual speech. As usual the subject is omitted; context determines whether this is directed at the addressee, a third party, or even ruefully the speaker.