Kind of, cockiness often goes hand in hand with toxicity. Riven players come to mind. I will not blanket statement and say all rivens but most rivens I have met over 7000 games have been cocky as all get up. Oh, i'm so good because I have no mana and since I have super low CDS, I can spam my abilities and can even animation cancel for super damage. Strong early so I can snowball and get ahead and 1 v 3. Spamming emotes, mastery, bragging about how good they are comes often. However, when things goes wrong, they all hurls insults, or decide to intent feed or afk because how dare it's their fault they lost or how dare they lose at all! They are really the only ones I will show mastery to when I outplay and kill them since they are, for the most part, very egocentric. The point is, when one has a big ego, it is easy to bruise it and set them off. Cockiness is poor sportsmanship but not really reportable unless they are badmouthing you, but it often leads to one being toxic down the road.