Let's look at McCree's numbers so we can better deal with him. McCree has 200 HP, a standard amount for defense and offense heroes. This means that critical shots from a Windowmaker or Hanzo will one shot him. His Peacekeeper is a force by itself dealing 35 damage at long distance, and 70 up close. While his Fan the Hammer cannot critically hit, all 6 rounds hitting a target in close quarters will deal 420 damage in 1 second. His combat roll is a key utility ability, reloading his Peacekeeper upon completion of the roll. It will move him 6 meters in the direction of his movement key, and has a 8 second cooldown. In 1v1 situations, McCree's Flashbang will stun you for .5 seconds dealing 25 damage, and be on cooldown for 10 seconds. Flashbang will automatically detonate at 5 meters or on any surface/hero, and if it does catch you his fan will deal 210 damage in that .5 second window.
Dead-Eye is one of the strongest ultimates in the game. Because he gains 160 damage per second that you stand in his Line of Sight, and it lasting 6 seconds, no target can survive this without hiding behind a wall or barrier. Even more, McCree's will not always use the ultimate on one or two heroes, but rather cancel it after 6 seconds retaining 50% of their ultimate charge and use the zoning power to press their advantage.