This was monday from a few weeks ago when the DOW dropped a thousand points intraday..
He was up $1.3M on 400-500 contracts short, then he picked a bottom and got long... the futures hit locked limit down, which is like a circuit breaker, and trading couldn't go past the hard boundary for a given period of time. He held his long through this period, and once the trading boundary lifted the market instantly started trading like 60 handles lower, instantly killing ~600k of his profits in a few seconds... the then gave up the rest of his profits just scalping and getting chopped up after that..
This was not a sim account.
He ended the day only up $21k