AD455 - the fall of the Roman west?

[Flavivs Aetivs]

In AD455 Valentinian III, last emperor of the direct Theodosian line, was murdered by a pair of Hunnic mercenaries.

Actually it's not stated what ethnicity they were. Their names were Optila (Occila) and Thraustila, which are Gothic. It's thought they were Huns because they were former buccellarii of Aetius, but they could very well have been Goths. Aetius inherited Pelagia/Boniface's buccellarii and likely also commander Placidia's buccellarii (the Placidi Valentiniani).

Yes, I did wonder about Majorian. It's a shame we don't know more about his victories, and the army he used to win them - the remains of the western field army, or largely barbarian foederati? For all his abilities, he does seem to have been largely under the power of Ricimer though, and his victories were brief and soon overturned. His campaigns - and those of Marcellinus and others - were more directed at recovering small amounts of lost territory. We could imagine that he - or Ricimer - with the help of eastern forces perhaps, might have turned the tide at some point and recovered Africa, or even Gaul, but they did not.

There may have been some Roman forces but the evidence says the majority of them were destroyed or deserted over the course of 451-455.

Avitus, Majorian, and Marcellinus' campaigns were an extension of one begun under Aetius in 453, where Aetius and Frederic retook Carthaginiensis from the Suebes with the ultimate goal of crossing the Gibraltar and retaking Africa, without Eastern assistance (Which wasn't available anyways since the East wouldn't recover from the Hun invasions until the 460's).