Some people are able to push themselves harder than others. They are able to tap into a reserve of strength and will and increase their strength and power. This however comes at a cost, leaving them weaker than before, but sometimes that is all you need.
These feats are called by many names such as Overdrive or Limit Breakers, but the common term is "Blood Feats". They are a way of pushing the mind, body and spirit further than normal but at a cost to health or something else. You achieve greatness now, but at a greater cost later. Which may injure you, or worse.
Some of the feats may be considered to be overpowered, so please think carefully before using them in your games.