and we saw Van Augur fighting big time. don't give such weird answer. if we are assuming between two characters, then it is safe and logical to assume Big Mom as stronger. she didn't become Yonko for nothing. we knew power level of two Yonko, that's the basis to assume for the other two.
it's not that we saw much of him, but we saw his ability. also as seen in shichibukai, some weird seductive power could be a abse for a yonko as well. if her power doesn't work in the range of his weapon, what then? again, One Piece is not about who is the "strongest". as I tried to show above, a sniper has quite diffrent means than strength, is that what was weird to you?
as for Caterina Devon, we never saw her fighting, good. so that's why we would assume her to be the looser? then why loads of characters without much info appeared in this tournament?
I think you're deliberately confusing something there. most of those are not my arguments, but what people wrote in the threads, just like I remarked exactly in this case. You might not have assumed her as looser, others did.
As for why these characters appear here, that's because they are considered fighters, still, if people don't want them in the tourney, they won't get there.
if you wanted to know popularity, then you should have said so. i would have voted for Robin too.
it's a fighting tournament, but we can hardly oblige anyone to vote that way - how would we control that anyway? that aside, naturally popularity does play a role in a tournament. ever seen a team going into gear 2 when the crowd cheered them on?
there are endless ways of arguing here, my favorite though is this is a "group fight" black beard would crush Kidd, take his DF and go to the next round with Robin - so what if someone wants to see it that way? Just the same with Tashigi.
you can stretch the tournament as far as you can; it will come straight down to them.
and exactly that is NOT the case. with crocodile and luffy or enel we saw just what's up in terms of DF and abilities. if any of those shichibukai or yonkou meet a character that has a bypassing ability they're out. period.
and your writing is very confusing. one time you say "if a tourney with the subjectively strongest characters is wanted we could just as well skip to yonko/shichibukai/admirals" and when we do assume for a character, you say "might be level 6, but was never really seen fighting. that's how I saw some argue in the respective thread and if people don't know her and don't want her in"
so what exactly is confusing you? as I said, with many of the reasons for the outcomes I wrote before I reflected what people wrote in the threads, just as the second sentence you were quoting.
. and there are users who are making an underground tournament,whose results are sent to MP. I didn't participate to that either,though.
(I'm participating and I find the idea pretty fun 
)
