Somebody’s pet hate
Definition 1 of 1
Pro Tip 1/3Personal Specifics
Refers to something uniquely irritating to an individual, not everyone. 
Mismatched socks might be your pet hate, but others may not care.
Pro Tip 2/3Not Literal Hate
Doesn't mean 'hate' in a strong sense, but rather an exaggeration for dislike. 
People saying 'literally' incorrectly is my pet hate, although it's just a small annoyance.
Pro Tip 3/3Conversational Context
Used in informal chats to express personal annoyances or quirks. 
In a casual meeting, Sara mentioned that her pet hate is when meetings start late.