I mean, it’s not that expensive to start an exit node, and requires “only” knowhow to mess with someone’s unencrypted browsing, which is what the first and third did. I can’t remember now if Onymous actually managed to break Tor anonymity - I’m pretty sure good-old-fashioned stings turned out to be a big part of it.

IIRC the two-node timing attack I was thinking of was an academic demonstration. Because it’s too non-specific to be very useful.