The word supplant means to replace can that mean in a bad way or a good way or even both?

Supplant has a deceitful or tricky connotation. The source of the word is interestingly from the bible, from a statement of Esau (Genesis 27:36) "Is not he rightly named Jacob? for he has supplanted me these two times; he took away my birthright; and, behold, now he has taken away my blessing."

The Hebrew word used in the bible for supplanted is "Vayeakveiki" which comes from the root word "Eikev" which means "heel" or sole of the foot. This is where Jacob got his Hebrew name "Yaakov" from (it shares the same root as the word "Eikev" (meaning 'heel').

In Genesis (25:26) Jacob received his name from his attempt at being the first of the twins to emerge from their mother, Rebbecca's womb: "and his hand took hold on Esau's heel; and his name was called Jacob".

This was the first contention between Esau and Jacob for the birthright.

The English word supplant comes from the Old French word "sub-planta" meaning "sole of the foot".

It appears from the biblical origin of this word that it has a negative connotation since it refers to Jacob's cunning and deceitful attempt at displacing Esau of his birthright as the firstborn.

Or the short answer: Supplant can mean to replace in a good way and a bad way. So you can use it both ways.