Giant, Stage 4 (Enormous Size)

Enormous Size. You go through another excruciating transformation of flesh and bone that concludes with you nearly doubling in size again. If your size is less than Huge, it is now Huge, and your reach increases by 5 feet. In addition, your maximum hit points increase by 20.

Flaw.
The Bigger You Are. Your prodigious size leaves you vulnerable to creatures whose size make them nearly beneath your notice. Creatures who are at least two size categories smaller than you (Small if you are Large, for example) score critical hits on a roll of 18, 19, or 20 on attack rolls against you. In addition, you cannot be immune to critical hits by any means.