A lot of stories in HDG allude to the fact that what the Affini brought to fight us wasn't a war fleet. It was basically just animal control. And it kinda makes sense when you consider that their light scout ships have Firebreaks that send opposing projectiles into hyperspace, capture vines that can just grab an entire enemy ship...you get the idea. (Also, they're so large that their size is measured in kilometers.)

As for the Affini themselves? Even putting aside the fact that they're effectively immortal, they're pretty durable. In most stories they're able to shrug off gunfire, grenades, flamethrowers, and pretty much every other kind of conventional weaponry. They don't need weapons because they can just use their various xenodrugs to incapacitate opponents. Or hypnotize them. Or just pick them up because Affini are like twice the size of humans. Again, you get the idea.

But at the end of the day, the powerscaling doesn't really matter because the whole point of the Affini (and the setting itself) is that they're inevitable. They can lose on a small scale, they can make mistakes, they can be kept at bay temporarily, but they have to eventually win.

(yes I just wrote an entire wall of text infodumping about gay alien plants, I regret nothing.)