The protagonist is presented as a veteran, but they're surprisingly inept despite this.
Alternate names: Incapable veteran, Inexperienced veteran
The first video game about Inept veteran was released in 1988.
Usually lampshaded via amnesia, some inexplicable strength loss (being severely wounded), being reincarnated, having had a drinking binge, etc. and they're now getting their mojo back, explaining also the rapid growth in how skilled they become, though fails if you have multiple characters in your team who along with you gain "power".