One-Punch Man - Tatsumaki, now actually looking like her age

Clockwork King actually had an excellent idea about why she's so small at her age, especially when you look at her younger sister. He theorized that the conditions the scientists kept her in during her youth resulted in malnutrition and stunted her growth severely. His idea holds water considering how mean she is to others and what she did to Genos when he called her a brat.