By default each action in combat has a 50% chance of success. So when you click on one of the attack actions (doesn't matter which one) it's a coin-toss to decide if you deal damage. Similarly for defending, 50-50 of not taking damage.
As Padder mentioned, pepperspray deals significant damage but you only get 3 per playthrough, so if you use them up on the early fights you'll have a harder time on the later fights. Pepperspray can kill the basic thugs in one hit, it'll deal 66% of total HP for the harder thugs.
As for "tricks" you have 3 options:
1. Fight the 2 layers of RNG across MANY fights, winning and losing as it happens (you're statistically more likely to lose), and living with the outcome.
2. Save scum, like Padder suggested. Save before each fight, reload if you don't get the outcome you want, repeat until all fights are done. Reliable, but very time consuming.
3. Cheat. There's a mod available on page 113 that Hotspot123 updated for us, and that I tweaked to make the Jamal fights easier regardless of which outcome you want (NTR, or non-NTR).
