Instructions
Give your character unnaturally high stats. Playable characters can only have a maximum of 18 in each of their ability scores, but the character you create can have as much as you want. For example, you can put double the amount of points in all of your abilities.
Assign many die to your character's hit die. Hit points are determined by rolling the specified number in the hit die section, so to give your character an unnaturally high amount of hit points, you must assign more die. For example, you can assign 40d100 to your hit die, meaning you must roll 40 100-sided die, the result of which defines your character's hit points.
Make your character an unnaturally high level. For example, if you make your character CR100, or a challenge rating of 100, this means he is a challenging fight to a party filled with level 100 characters. Most party members cap at about a fifth of that level.
Make your character multiple races. For example, a part dragon, part undead character gets you access to Draconic and certain Vile feats, such as Baleful Moan, which would otherwise not be available if your character weren't a dragon or undead.