La regué is a popular Mexican slang phrase that means "I messed up" or "I blew it". It's a super common and natural way to admit you've made a big mistake.
The verb regar literally means "to water," as in watering a plant. The expression likely comes from the idea of spilling water and making a mess, a perfect metaphor for messing things up!
In "TE ODIO!", the singer says, "Contigo neta que la regué" ("With you, I really messed up"), expressing his raw regret over getting into a relationship that ended in heartbreak.
This song is one big, emotional late-night phone call to an ex. The singer is completely heartbroken and confused after a sudden breakup. He can't believe she left him for someone else, and he's not shy about his opinion on her new choice: "¿Por qué lo que escogiste a él? / Neta que bajaste de nivel" (Why did you choose him? / Honestly, you lowered your standards). He swings from love to hate, admitting "Te amé y ahora te odio tanto / Me rompiste en pedazos" (I loved you and now I hate you so much / You broke me into pieces). The hate is so intense that it physically hurts him.
He's not just sad, he's angry and looking for answers. He wants to know exactly what he did wrong, asking "Quiero que me digas en qué fallé" (I want you to tell me where I went wrong). He even throws in the ultimate guilt trip by mentioning that his mom liked her too! He plans to burn all her photos and just cry over the memories. The feeling is summed up perfectly in one brutally honest line: "No te deseo mal, pero tampoco bien" (I don't wish you bad, but not well either). It's the perfect song for when you're feeling hurt and a little bit petty.