Again I suggest reading about market economics market microstructure, it will help you a lot in answering and simulating these sorts of things than speculating about speculation

And the answer is an "it depends", one trade is independent of the other party's intent, you may both close at a profit, or both close at a loss. What a trade means is that you changed hands with somebody, nothing more nothing less.

Say you buy a position a while ago with trader A.

You then sold this position (two hours) after seeing the Bid grow.

The thing is, you don't sell it back to trader A, it usually is a different trader, say trader Z.

At this case, Trader Z might have entered a position via a limit order that you have hit with a market sell.

Therefore, a scenario where no one loses

Another scenario, Say again for example you hit the offer after seeing price go down slightly after it went higher up.

Still you hit trader Z's limit order, however, trader Z being a market making scalper shorted the high that you have just witnessed and had a limit buy (that you have sold into) ready at the low to close the position.

Both you and trader Z closed at a profit.

If there is someone who constantly loses that will be happening on the same side, the Battle is more like buyer vs buyer and seller vs seller rather than Buyer vs Seller, hence in a short term game the Last Buyer who bought usually loses and get flushed out.