This is Base Thanos without IG, CC or HOTU.
Yhwach has access to all sternritter abilities, Yamamoto's Bankai, the Almighty, he also has access to his father's (SK's) feats from the CFYOW novels.
Round 1: speed is equal
Round 2: speed is unequal
Win by death, both are IC but determined to win
Edit: Yhwach still has access to his daddy's feats, however he is now bound by coventional life and death and CAN be killed by conventional means.