The Stamina Stat is a stat that adds to base health maximum of 100% in Strife. You can potentially reach 200% health. The higher the stamina, the more likely the Punch Dagger will kill higher level monsters in fewer hits. Some players have even stated they can kill an Inquisitor in one lucky Dagger punch at a 90 Stamina stat or higher. This tends to make the Punch Dagger more and more favored in many levels of Strife. The additional health makes the Sigil more viable, especially as it consumes more health with each Sigil piece. The Surgery Kit's effectiveness becomes much more appreciated with the higher Stamina, since it will fully recover a player per use.
The maximum stamina value a player could have is 100.