I can't say a sweeping statement other than it appears INFPs can be very bitter and resentful. Like an Eeyore complex, when unhealthy.
But then the healthy ones show such amazing strength and fortitude.
This sounds right. I think the unhealthy ones kind of have a blind spot to the bitter vibe they're putting out, and they assume that the world itself is the problem. "I'm a really great guy, but apparently girls don't want a nice guy" kinda thing.
There are some really great INFPs around, of course, but that wasn't the idea of the OP, so I'll just leave it at that.