Based on the level of respect or formality, you can say "You're going to be awesome!" in Korean in 3 ways:

• Informal: neo-neun choigo-ga doilggeoya! (너는 최고가 될꺼야!)
• Formal: dangsin-eun choigo-ga doilggeoyeyo! (당신은 최고가 될꺼예요!), dangsin-eun choigo-ga doilggeopnida! (당신은 최고가 될껍니다!)
• Very Formal: dangsin-ggeseo-neun choigo-ga doisilggeopnida! (당신께서는 최고가 되실껍니다!)

- you (subjective): ne-ga (네가), ni-ga (니가), neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는)
- to be going to be: doil geot ida (될 것 이다)
- awesome: choigo-eui (최고의), duryeo-un (두려운)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.