Malimpusiste is a fascinating and somewhat rare word that combines "mal" (badly/wrongly) with a form of "imponer" (to impose). It's not a standard dictionary word you'd find easily, but its meaning is clear in context.
In the song, it describes how the singer feels his lover wrongly accustomed him to her kisses and caresses, only to leave him. It conveys a sense of being unfairly led on and then abandoned, making it a unique and emotionally charged word.
Have you ever been so mad at someone for leaving, but deep down, you know you'd probably forgive them? That's exactly what Banda MS is singing about in "Altamente Probable"! The singer is really upset, asking, "Para qué malimpusiste a mi boca / Para qué la besabas de esa forma / Si al final te ibas a ir?" [Why did you impose on my mouth / Why did you kiss it that way / If in the end you were going to leave?]. He feels like his body was also led on, taken "hasta el cielo" [to heaven] with caresses, only to be told goodbye.
He knows he's in a dangerous place because "Las botellas de alcohol son un peligro" [Bottles of alcohol are a danger], and he might just empty them out of spite. And if he does, he admits, "Voy a correr a irte a buscar" [I'm going to run to go look for you]. Even though he's suffering, especially with photos bringing back memories, he confesses that his feelings are "tan incondicional" [so unconditional]. So, despite all the hurt, he concludes, "Es altamente probable / Que te pueda perdonar" [It's highly probable / That I can forgive you]. It's a classic tale of love, anger, and the surprising power of forgiveness, even when you don't want to give it!