From the Super Mario Wiki
Mad Big Boos are enemies in Super Princess Peach and can be found in Shriek Mansion. Like their smaller counterparts, Mad Big Boos are the opposite of normal Big Boos: when Peach is not looking at one, it will stop moving, and when she looks at it, it will quickly move towards her. Like other Big Boos, they cannot be defeated by Rage.
One of the levels in Shriek Mansion has a Big Boo and Mad Big Boo, meaning that Peach will be chased no matter which way she looks.
Names in other languages
||Boo Atomique Enragé
||Enraged Atomic Boo