I think every superhero needs a weakness. If they are unbeatable then they are not interesting. I think weaknesses that are tied to their powers are ALWAYS more interesting. Of course the weakness must be such that your average joe could not solo them. If a thug with a gun can kill you, then your not super. I think you should be able to survive that at least.
Here is my OC with her weakness included, WHAT ABOUT YOU?
Frog leaping: Frogs leap far because their legs have what are like springs that recoil when they jump, propelling them forward. Some frogs have been known to jump what would be equivalent to a human jumping the length of a football field. Kribbit can do that with her biggest jumps.
Skin Toxin: Like a frog she can secrete liquid toxin from her skin that can be deadly to average humans if she makes it potent enough. It looks like sweat on her.
Frog Like Tongue: She can shoot tongue out 10 feet and catch stuff with it. She can wrap it around stuff too.
Strength/Durablity: She can lift 5 tons max. She would strain if she tried to lift that for long. 4 tons or less is easy.
Universal Magnetism: Useful for sticking to walls even while wearing clothes over the skin. She also uses it to easily grip and pick up heavy things.
Her weakness: Tied to her strength. If she tries to lift more than she can her powers will cancel out, making her mortal. So throw a semi at her and it would probably kill her if it weighs over 5 tons. However she would likely jump out of the way : )
Even with her durability she can be knocked around. She would not just tank bullets, she would fall if hit, just not be killed. Because like a frog her body temp is like outside temp, a freeze gun would freeze her solid. Although it would not kill her (that's how some frogs hibernate) it would definitely put her down till she thawed out. Suffocation could kill her if someone was strong enough to actually choke her.