Vaam wins. Additionally, though,
Many people seem to miss several important caveats.
Yeah, immortality contract can still let FHs survive after 'anything', but that is not the whole point of being a threat.
1-] FH has families. Even though at minimum, they have some care, to their descendants or regents via giving shinheuhs, items, whatnot, as well. If someone waltz in and one shot not only Proust but also your ship, even if you have the immortality contract that is still bad. Gustang may not care much about his creations or Proust but he still tries to manage a family, and as for Traumerei, we have seen that he at least cared about Kirin, Robadon. In short, you can be a threat by just tremendously messing up with your family there. So, Adori is a threat.
2-] At least for once, Traumerei complained Gustang about how he was ditched because after some point in their climb, they decided to care only about the relationships among them (I believe after V-Arlene separation) while Gustang apparently a psycho and did not. Gustang is ditched and all already, so Adori attacking Po Bidau does not mean much, but any person that can have a detrimental impact on the relationships between FHs is a threat. Remember Ha Yuri Zahard's "bad" treatment after the last station and Ha's reaction. Yuri is not a super high ranker, not really super above anyone, but terribly important as she may result in a serious conflict between FHs (even without she himself trying to sow a one). So, Yuri is a threat, and probably V is a threat because of this, too.
3-] As long as Urek does not take action against FHs, FHs themselves did not seem to do much, like Gustang just talking to him. Comparatively weaker and so very most probably a regular Luslec, (hence no hack against immortality) was more in their eyes. Of course, only Luslec himself was not the threat here, whether or not he can be a nuisance, potential Arlene and real V and Baam influences makes Luslec more than what he can individually muster. One minute detail, Arie Hon was a recluse at the time of Ameuz's departure, did not greet Eduan and Eduan jokingly attacked him etc, but he went out and told Luslec to ask about Arlene. Also, a reread of FoD had an interesting part where Urek explains how he stole Red Thryssa and Hell Joe separator injection liquid from a F.U.G. base. Urek's not storming but stealing is one thing, F.U.G. making/having such things another. So, Luslec is a threat.
It saddens me that we talk about only arm wrestling here and there.