Batallosa is a colloquial, fairly unique word built from 'batalla', meaning 'battle'. It describes a person who is difficult, argumentative, or constantly causing drama, someone who turns every situation into a fight.
The singer uses it to call out this kind of troublesome person, singing about dealing with someone "batallosa" ("a troublemaker") who makes everything harder than it needs to be. The word paints a vivid picture of someone exhausting to be around, always stirring up conflict.
In "Aunque Te Duela," which translates to "Even If It Hurts You," Edgardo Nunez delivers a brutally honest warning to someone who is falling for him. He doesn't sugarcoat his intentions; instead, he lays his cards on the table, calling himself an "expert at breaking hearts" and admitting he simply doesn't want to love. He urges the person to walk away before it's too late, not because he's being mean, but because he doesn't want to hurt them.
The singer makes it clear that he isn't going to change. He advises the other person to "start valuing yourself" and find someone who will truly love and respect them. He confesses he's the type of person who will "promise the stars / but wouldn't bring down a single one for you." The song is a powerful message about knowing your own limitations in a relationship and telling someone the hard truth to save them from future pain.