You played it bad and now complain about RNG? Seems kinda ridiculous to me, isnt it?
As guys above said, you are not suposed to keep strong cards for last play while your opponent has double cross ready, if you do, you are giving a lot of value to your opponent. This particular case has absolutely nothing to do with RNG. You ,,cooked,, it up for yourself so you had to ,,eat,, it too. Learn from your mistakes
I had some actual bad RNG though, like that time i played vs nilfgaard with my Foltest deck. Initial draws were kinda bad, most of my hand were broznes or midrangy golds, all of my power plays in deck. I was like, hmm, this round is probably lost, lets play some weaker cards and pass, but then the RNG happened. My opponent played vigo into viper witcher turn one and banished my roche merciless ( i had 2 comandos in that deck but no scouts) so one powerfull combo gone. Next turn another viper witcher, banished my seltkirk. Next turn the same and banished my princ anseis + emhyr onto one of the viper witchers which banished my queen adalia. In 3 turns most of my power plays gone, i had nothing to use my foltest on ( maybe some bronzes for 2 dmg... while my opponent played a few cheap bronzes. That was bad RNG on my side a good rng on my opponents side. I forteited that match after those 3 turns, there was no hope of winning after that... That felt bad, but at least it was fast and my opponent probably had a good laugh while banishing all of my expensive golds.
The thing with RNG is, that it works both ways, when it screws you, it helps your opponent at the same time and the other way around. People tend to remember and talk about the BAD RNG and very often forget that the GOOD RNG happens to them too. It might feel like you only a have a bad luck, but if you ask me, i think its 50/50.
I think RNG is not the bad thing to have in the game, especially game like this. It creates hilarious situations, can win you seemingly unwinnable games etc. Think about that a bit