41ada8fe_Squid_Girl___Squid_Girl_Wiki__Explanation
[Weakness] Fear of being experimented on by Cindy Campbell and her fellow researchers. [Explanation] 
Campbell believes that Squid Girl is an alien, and pesters Squid Girl since she wants to experiment on her. However, Squid Girl doesn't want to be experimented on.
Squid Girl - Squid Girl Wiki
Explanation