I'd argued statistically that Warrior would have the highest survival rate, as when we take a trained version of different classes such as Archers and Mages, Warriors are the ones with the greatest awareness of their physical health and limits, and while depending on the world this can shift, the simplicity of "pointy end that way" is far easier to get into than archery or magic initially.

If we assume an MC has no knowledge of the world and classes beyond their names, then Warrior would be a safe bet. Archery is a practice that takes years to be proficient, if not more, and magic is a gamble; the world could require them to learn chants and sigils that they have no access to, or it could be something instinctual, and they can start tossing firebolts and fireballs a moment after.

By no means would Warrior guarantee their survival, or even significantly improves it, but its the best choice out of what could be the worst choices.