Those who had been or are in the competitive side of gaming will mostly relate, a One Main Wonder is, in simpler terms: an individual who can only win if said individual is using her/his main, they can be easily spotted by their lack of ability or lack of interest in learning to use different characters, or has been playing that character for too long and is stuck in a zone of comfort, this however brings a much extense debate whenever it is ok or not to be a O.M.W. but it all comes down to what kind of game they play, for Fighting games, One Main Wonders are not much of a problem, all it takes is the right character to counter his/her character, on online competitive however (LOL, OW, FORTNITE, SSBU and so on...) can be a problem, you play to support your team and carry out your role effectively in order to acchieve victory, if a One Main Wonder can only use a character that does not fit the role your team needs, you will have a hard time battling the enemy.