Sertorius.
We don't know a ton about his family; they seem to be equestrians, but not particularly notable. He became a career military man, serving in, and surviving, the Battle of Arausio, which was a huge Roman defeat by the Cimbri and Teutones.
He later served under Marius, and became attached to the Marian/Cinnan party during the civil wars against Sulla.
Sertorius found himself in command of an army guarding Rome when Sulla came back from the East and began his second march on the city. Sertorius judged that he was completely outclassed by Sulla's veteran army, and noped out to Spain. The Sullan party pursued Sertorius constantly, wearing down his last few troops until he was forced to abandon Spain. He joined some pirates, visited the Canary Islands, and eventually took his surviving force to Africa.
While the Sullans were chasing him into the interior of Africa, he got very, very sick. When he recovered, he had a new plan. He took his remaining soldiers, evaded the pursuing Sullans, made it back to the North African coast, stole a fleet and launched an amphibious night-time invasion of Spain.
This time he had the support of the locals, and he trained them in Roman style fighting, using his few remaining Roman soldiers as officers. He established schools for the kids of the local aristocracy, and found a pet deer that supposedly brought him intel on his enemies (Plutarch says this was a completely cynical fabrication on Sertorius' part, but the locals bought it and it led them to believe Sertorius had divine support).
He mopped the floor with every army the Sullans in Rome sent against him for seven years. Even Pompey couldn't get a handle on this guy.
In the end, Sertorius' officers assassinated him for reasons that are not entirely clear. After capturing Sertorius' camp, Pompey weirdly burnt Sertorius' papers and correspondence unopened and unread. There's some suspicion that Sertorius was engaged in negotiations with some people in Rome looking to secure a return to the city and a restoration of the Marian party, and just maybe Pompey might have been one of those people.
The only other man Pompey couldn't beat was Caesar, and even Caesar took a strategic, if not catastrophic, loss at Dyrrhachium.
If I ever write my sword-and-sandal historical novel, it's going to be about Sertorius. The whole story seems very Heart of Darkness or Apocalypse Now
It's unusual for a Roman emperor to be considered a god before death. Caligula tried that and it was a disaster. But even Constantine was deified after his death, despite his conversion.
As for the sincerity of Constantine's conversion, the previous generation of scholars, people like Aldofi, MacMullen, and Barnes, tended to take it pretty seriously. Hal Drake in 2002 (relatively recent in terms of ancient scholarship) thought Constantine took a much more politic view of Christianity and indeed was making political choices rather than choices of religious conviction. His student Digeser, who was my diss advisor, has her own book coming out in which she argues that Constantine is coopting Christian rhetoric as well as the power structure of the Church to secure his own policies and positions. But I don't know when that book will be published.