Gary Stu
The boring male protagonist who always overpowers his opponents without paying any price or breaking a sweat,haves no weaknesses,haves generic character design,bland and poor personality and doesn't have guts to marry a girl or even to do any adult stuff when girl who loves him want him to.
Kirito from Sword Art Online is not a Gary Stu. Take a look at Touya Mochizuki from In Another World With My Smartphone. He is true definition of Gary Stu,the god of Gary Stus. This protagonist have infinite mana,always overpowers his enemies without taking injuries,bleeding or paying any price for his powers,his personality doesn't have any strong or enjoyable features,his character design is generic and he hesitates to marry girls who love him because he is clinging to morals from his old world and he doesn't have guts to do a hard thing. Kirito pays price for his powers and struggles in almost every fight and he have more personality than generic isekai virgins like Touya Mochizuki.