Leaving this here really quick before i go to bed cause the other thread reminded me of it.
Premise: A simple template that says "WHO WOULD WIN?" at the top and then divided in half. Two parties are presented, one has a clear advantage over the other. Replies generally consist of explaining how the disadvantaged party comes out on top.
Seems to be a 4chan thing mostly, although a couple google searches return some spread to reddit, including a whole subreddit that seems to repost many of the popular 4chan ones in self-post format, although most of the posts are more serious
Examples:
The lions vs the sun one in particular seems to be rather popular and is reposted quite frequently since sometime around the 15th of January.
edited to add the subreddit link i missed apparently. i really should sleep goodnight