Repulsive Reptile

Leon. The brawler's that's been a menace since global release still manages to stay fairly relevant in competitive play.
Leon has an impressive maximum 11.5k damage burst with his bar filled, which allows him to "effectively" kill any brawler in the game from close range (except Frank, but no one sane plays Frank in competitive to your benefit.)
Of course, that implies you get close enough to practically merge with the enemy brawler, which has its ups and downs. This build is balanced to max out the utility of your super - granting you some form of pseudo-regen and increasing its duration to capitalize on it as much as possible.
Leon doesn't have a lot of health, and when he's caught you'll usually get into the red quite fast so use your super to either escape or change your route and turn the fight around.
Lollipop Drop is used to give both you and your teammates a certified Jumpscare Area® or a way to pass into some bushes unnoticed for ~23 seconds. Try to not put it in plain sight since it's easy to break.Counters:
Getting caught - Self explanatory. If the enemy team is equipped and smart enough to counter your entire gimmick you won't be able to do much, especially if they constantly stay at a distance.
Mobile brawlers - Brawlers with dashes and other escape tools can get out of your effective area the second they spot you, and due to how your attack damage scales you will feel a drastic decrease in damage the further they get. (max 960 - min 287!!! per projectile)
Bad maps - Maps without a good amount of bushes, wide sight areas or too many walls impede you from reaching enemy brawlers without being riddled full of holes. And no, your Invisiheal won't save you if you can't even charge it up.