Though his personality isn't directly shown, you can gather what it is like by playing the games and reading the manga. Nintendo and Retro does a good job of indirectly stating his backstory and personality.
His origins are quite cliche, yet he is still a very interesting character. He was born on Zebes to a tribe of bloodthirsty creatures that were armed with razor-sharp teeth, deadly claws, and an almost metal-piercing tail. These creatures had many interesting attributes; for instance, they cannot die by old age. They are in some ways similar to a phoenix. Their dragon-like body is just a single host they use for protection; but the real life essence is under the skin. When one of their own is killed, the life essence is released from the dead carcass in the form of a ghastly ectoplasmic monster. This monster roams the area near their carcass to search for other dead organisms. It then devours the dead skin cells of decaying beasts, and those cells are recycled to produce yet another dragon-like body. This here is your straight-forward explanation to how Ridley comes back from the dead. It also explains why the Galactic Federation froze him in a cryogenic chamber in Metroid Fusion; if he's frozen, how will he ever come back? His body isn't dead, and the ectoplasmic beast can't leave a live body it's inhabiting.
Ridley's race was killed all but him by the Chozo for being a nuissance. It is unknown how the Chozo pulled this off, but likely that they restricted the beasts into some Chozo statues, therefore explaining how Torizo's are "living". Ridley joined forces with Kraid, a member of a large lizard race who was almost entirely wiped out from an unknown plague that spread through Brinstar at one point; only Kraid and a few of his smaller variants survived. Ridley and Kraid stole metal from the Chozo to build a ship, therefore soon building the Space Pirate Empire and creating yet another nuissance that which the galaxy would suffer from.
Ridley has done many deeds that play large parts in the overall story of Metroid. For example, if Ridley hadn't killed Samus's mother and raided the planet, Samus would be living life as a housewife when she got older, due to the fact that she would have never been raised by the Chozo, and therefore would not have their blood in her bloodstream that made her strong and flexible. Ridley, in a way, created his own nemesis. And he also pulled a scam with Mother Brain, thanks to Grey Voice allowing him to. Ridley falsely promised Mother Brain that it would reign almighty, and gain revenge on Samus for the quarrels it had with her. Ridley truly meant to scam Mother Brain, and made the galaxy think that it was leader of the Space Pirates, so who would the Galactic Federation target instead? Mother Brain. Why did he do this? To buy time. He bought even more time by not only bringing Mother Brain into the situation a second time (Super Metroid) but throwing himself in the way of Samus's path both of those times. But it wasn't enough to keep Samus from prevailing. Ridley, in the end, lost, as after his second defeat on Zebes, he gained a new body, and was taken by the Galactic Federation to be frozen in the cryogenic chamber he was found in in Metroid Fusion. The X Parasite mimicked Ridley, and created Ridley X, which is commonly confused with the real Ridley.