Easy to spell, high value name with excellent connotations ("supreme" as an adjective means "very great or the greatest").
The word "supremer" contains eight characters and three syllables. Successful brands using three syllable names include Armani, McDonald's and Mastercard.
Supremer.com is a .com domain. Dot com is the most desirable domain extension. Once you own a .com, it will be much easier to rank for your own name in Google.