He's a Bounty Hunter: Greedo works for Jabba the Hutt, hunting down criminals and debtors. This puts him in a position of enforcing the law, but often in a ruthless and cruel way.
He Tried to Kill Han Solo: Greedo was hired to assassinate Han Solo for owing Jabba money. While Han was a smuggler and had done wrong, Greedo's attempt was still a direct act of violence.
He Was Out to Get Han First: In the original film, it's Greedo who fires first at Han, even though Han was drinking and seemingly unaware of the threat. This makes him seem more aggressive and less justified in his actions.
However: Some fans argue that Greedo's portrayal in the special edition, where Han shoots first, unfairly paints Greedo as the villain. This change has been criticized as making Han look more heroic and Greedo more evil than was intended in the original film.
Ultimately: While Greedo is clearly not a hero, his role as a villain is open to interpretation. Some argue that he was simply following his orders, while others see him as a ruthless criminal.
In the broader Star Wars universe: Greedo's character serves as a representation of the dark side of the galaxy, highlighting the dangers of violence and greed.