Wasn't it mentioned somewhere that VOY could draw power from Nebula matter and energies given off by stars? That's standard sci-fi power-generation stuff.
If you're talking about The Cloud, or that time with the selenium when they busted up that shuttle... That was a mining operation, sure they used something akin to a buzzscoop ramjet to get what they needed, but it was a proccess a little more difficult than "power" just being ambiantly collected from general particulate matter and energy.
Better than Dallas, worse than Mana.
And in so far as forgiving people for trying to kill and imprison you? Or tolerating traitors to your political system? The Irish and English get along "fine" these days and it only took 900 years for it to all lull into the current lack of exceptional slaughter.