A question came up, could you please help me sort it out?

A question came up, could you please help me sort it out?

A stranger is OPing for me and my friends in PbP. During play I raised my character unstated 'power level' to be able to beat his enemies because the situation looked diresome (the rogues against a whole city state). The OP did the same because he felt that we are slaying our enemies like flies. We basically tried to match each other a couple of times and this created a frustrating loop. We realized this conflict of agendas but could find any written principles on what to do and how to solve this problem.

I've always thought that in the end rogue players have nearly full control of what is weaker and what is stronger than them. I played a shitload of Sw/oM but I'm not sure if I say this from a flawed conviction.