Lal Mirch is one of the Arcobaleno from Katekyo Hitman Reborn! She intended to take the place of Colonello, but he showed up anyway and so her pacifier is grey and incomplete.
Lal is shown repeatedly to be a major badass. She is skilled as a soldier and can use Rain flames to power her attacks. She trains Tsuna to prepare to invade Melone base during the Future Arc.
She is blunt and calls it like it is, and is not one to take Tsuna's self-deprecating nonsense or his can't-do attitude. She is willing to get physical to get the team up to snuff.
Because of her incomplete curse, she feels that she cannot uphold her duty as an arcobaleno, and considers herself their weakest member. That is anything but true, however.
Lal's greatest strength comes from how deeply she cares for her comrades. She loves the people around her more than anything. That is what makes her powerful. And badass.