You cannot run. You cannot hide. There is no terrifying hunter in the game than Leon. Once he's targetted you, running away is impossible, especially due to his abilities. Tracker's Blade will chase after you, and once it strikes, the hunt begins. His Tracker's Frenzy will ensure that he will outspeed you, and once he catches you, you're done for. This doesn't include his powerful Plasma Blast, leaving behind a fresh burning pile of heroes in it's wake. Be careful when you turn your back to him, or he will punish you with Slice Achilles' Heel.
Leon's runeset prioritizes his ability to rain non-stop attacks on his foes. His best weapon is his basic attack, which means he has a number of runes that increases his ability to do so, while his other runes complement that by disabling his foes with a number of effects, primarily slowing his hunt down or speeding him up to make sure he can't be escaped.