Basically where they challenge each other to a sexual stamina contest - which means whoever cums first loses. An example of it would be (link removed)

Thanks in advance

Hmm..

Two that came immediately to my mind are these two oneshots by Kusanyagi's Translation Corner.

Dissonance chap 1
Futaboko Co - Aurora chap 2

Neither of these seem to have a MU page to link to. They are slightly on the darker side of things, but nothing actually brutal. They feature funatanari in some kind of gladiator fighting sex-thing where even physical pain is translated to sexual pleasure and the winner is determined by fucking and/or wrestling the opposition to the point of fainting.

Not quite what you mentioned in OP, but definitely a case of sexual stamina contest 😛

The final chapter of Safety Lodging House Utopian is a good entry

And if my memory isn't completely addled Brandish has this on some of the chapters. Usually they go for quite a few rounds though.

Oh yeah. You might want to remove that link, neighbor. MU rules don't allow linking to readers.

[img]http://i2.kym-cdn.com/photos/images/original/000/028/438/5700.necropost4kobf7.png[/img]

Thanks a lot man - removed link btw