Compite comes from the verb competir, meaning "to compete". While "compete" is a common concept, its use here is particularly engaging.
In the song, Becky G sings, "He estado con otros, pero a ti nadie te compite" (I've been with others, but no one competes with you). This line highlights the unique and unparalleled allure of the person she's singing to, making it a strong and memorable word in the context of the lyrics.
Becky G spends this whole song refusing to say the one thing her ex wants to hear. "I don't love you, no", and then straight away "Pero casi" (but almost). She keeps doing it: "He estado con otros" (I've been with others), followed immediately by "Pero a ti nadie te compite" (but nobody competes with you). It is a booty call written as a negotiation, and she is the one setting the terms.
The hook lands the compliment on herself rather than on him. "Encima de ti / Yo me veo más pretty" (on top of you, I look prettier). She wants the light left on for it too: "No vayas a apagar la luz / Pa' que veas how I climb on top of you" (don't go turning off the light, so you can see how I climb on top of you), a line that flips from Spanish to English halfway through, which is how the whole song is built. At just over two minutes it says what it came to say and leaves.