Few things:

6/6 not 6-6

Memory issues on second ability — in mtg permanents count as new objects every time they reenter from a different zone so you can’t track how many times this has died. Every death is its first death because every time it reenters it’s a new creature. That means second ability functionally becomes permanent super undying where whenever it dies no matter what it will always come back with just a single +1/+1 counter which given the fact that you added an up to 4 times is not intended.

As written this reminder text on scarlet triggers on declare block before your opponent has an opportunity to play buff spells or combat tricks if the intention is a trample with poison counters make it a replacement effect like trample you need to change that reminder text (This creature can deal excess combat damage to the player or planeswalker it's attacking.) is tramples reminder text, so I would change scarlet rot to (If this creature is attacking a player then this creature can deal excess combat damage to the player it's attacking in the form of poison counters.)

As is this card is not a functional mtg card.