A Japanese manga i happened to find a few months ago was Morumo. It wasnt in English, but i noticed a lot of strength scenes. It's about a giant alien girl who is 50 feet tall and receives a serum which makes her normal sized. The catch is she still has the same weight and density of someone who is 50 feet tall. This means she is super-strong and indestructible when she is normal sized.
The entire comic can be found on this site:
Note that this is a Geocities site and it has a bandwidth limit.