20:18 is saying, "path of least resistance" which is another way of saying, the better or easier option. At 18:38 he says "...who can say they're "o" in four right now..." this is an expression meaning "zero in four" or 0/4. "O" is slang for the number "zero", and it is often used when talking about a certain score. I haven't seen this episode, but I'm assuming he is saying that he has not lost at all in the 4 rounds so far, or that he has zero losses out of the four rounds.

18:38 "oh and four" oh like zero.. He should have said "oh for four." It means he's had 4 chances to win and failed all of them. 20:18 "path of least resistance" but he did not say it clearly. Path of least resistance means "the easiest way" to do something. He was saying that the others in the group will get rid of him because he is the easiest one to get rid of.