Cruelty to animals by young kids, especially if it happens only once, is sometimes a reflection of developmental immaturity. A pattern like you report is more serious and is sometimes the first indication of conduct disorder. In your case, it may have been a way to channel anger that felt overwhelming. In most kids, the pattern drops off after adolescence. But some kids who torture animals as children develop into adults who are violent with other people.
You are now 20. You didn’t mention if the pattern continues or if you are now re-evaluating things you did as a child and teen. If you still feel the urge to treat living beings (animals and people) cruelly, violently, or disrespectfully, you have a problem that needs to be addressed. Treatment now can help you manage anger constructively and develop more empathy for others. This is the key to living successfully in the social world and having satisfying, and safe, relationships. If you now feel terrible for behaving as you did and would never do such a thing again, then you somehow grew out of it on your own to be a more moral and decent person.
I wish you well.