Tú soy la mejor persona que he conocido. correct incorrect

This statement is incorrect.
The cause of this is that the second word 'soy' does not make sense and does not have a place in this sentence.

This sentence originally means : You I the best person I have ever met.
As you can see, this sentence does not make sense with word 'soy' in it.

If you change the word 'soy' to 'eres' the sentence will make much more sense : 

Tu eres la mejor persona que he conocido.
means
You are the best person I have ever met.

I hope this helped - Maria S.