When you reach a level...
As you level up you become stronger of course, but always remember that no matter how strong you get you can NEVER be invincible. Why is this? Well first of all even if you are about 15 levels higher than your opponent let's say you got hit in the back 10 times in a row and we fireballed into the ground then you LOSE. I don't care what you say NOBODY survives that!
Leveling Abilities
As you level up you learn abilities that can help you in battle such as Transforming, going SSJ, or just plain going nuts on your opponent with everything you have. HOWEVER there is a limit to each of these abilities, it wouldn't be fair for you to fight someone that transformed under a full moon and the instant the fight began he transformed now would it? To read about the limitations of abilities go to the Abilities Page.