Scarlett and Hiram :
Scarlett gets very competitive over small things. Hiram starts a debate? She is right he is wrong, debate over. Scarlett has a very hard time admitting she is wrong, and when Scarlett is right she will hammer it into your skull. There have been times where Hiram has had to say "this is not a debate, this is fact" to keep her from needing to be right. Someone has issues from having Welles as a babysitter.

Kira and Sanjar :
Kira is competitive with everyone except Sanjar. She got protective and possessive fast. When she realized she could trust him, she didn't want to lose him or see him hurt. However anyone else challenges her to anything she gets dangerously competitive. Drinking competition? Sanjar has to get worried cause she's had six spectrum vodkas and she's not slowing down. Hunting? She's coming back bloodied and bruised dragging back manti-queen corpses. She will win or die trying. However if it's Sanjar she can't bring herself to be competitive. She'll let him win but in a way where it looks like her really tried.