"Selfish" already incorporates the prefix "self-", which signifies that the word is centered on the individual.
If you're looking to describe different aspects of selfishness, you can use other words or phrases instead of prefixes:
* Extreme selfishness: *egocentric, narcissistic, self-absorbed, self-centered*
* Selfishness focused on material gain: *greedy, avaricious, covetous*
* Selfishness motivated by cruelty: *malicious, vindictive, spiteful*
Remember, using specific words and phrases can help you express your intended meaning more precisely than simply adding a prefix to "selfish."