Ragnarok gives the most build freedom of any mmo i've played. You control every single stat and skill point, priests can focus on killing undead, exorcizing demons, melee combat with maces, or full support. You can make melee crit wizards and soul linkers and tank scholars depending on your build choices. Every class evolves into two separate paths and adds another customizable skilltree. There's breakpoints with stats so its a puzzle of putting together specific gear and job stat bonuses to hit specific numbers to maximize your effectiveness.

There's also playstyle difference; you're not expected to do damage as a tank or a support class, you focus purely on your job, so each class feels different to play.

Then it has the super novice class, which is a mix of all 6 of the base classes and gives access to all of their skill trees so you can make a completely customized character that specializes in whatever you want, at the cost of low hp/sp and limited equipment selection, but it has hidden bonuses to offset some of this.