After T'Challa returned following his father's death, M'Baku was conflicted if to challenge him for the throne, although he would side with him when Erik Killmonger, T'Challa's cousin, threatened Wakanda and would become king for a short time, after T'Challa's apparent death. Seeing what Erik had done, M'Baku chose to save T'Challa's life and would join him and other Wakandians to defeat Killmonger, which led to his death.
Two years after Killmonger's defeat, the Wakandians learnt of Thanos, a warlord planning to use the Infinity Stones to erase half of the universe from existance. M'Baku joined the king and his allies, including some of the Avengers, to fight against Thanos' army. Although they were unsuccessful and Thanos erased 50% of the universe, but M'Baku survived.
Five years later in 2023, after the Avengers gained a new infinity gautlet, after time travelling, M'Baku joined the resurrected heroes to battle Thanos during the battle of earth. The heroes won after Iron Man sacrificed his life by erasing Thanos and his army from existence, by using the infinity stones.
Several months following the death of Iron Man and Thanos' defeat, the Wakandians learn that their king, T'Challa, has been diagnosed with an undisclosed illness and eventually dies, despite his sister, Shuri's best efforts to recreate the heart shaped herb to save him. M'Baku attends his king's funeral and supports the family with the loss. The following year, Wakanda is attacked by a sea warrior named Namor, Namor threatens the Wakandians and floods the whole country, which leads to Queen Ramonda's death, much to Shuri's despair. After Shuri decides to become the next Black Panther, M'Baku challenges her strength before accepting her. In the end, Shuri and Namor make a truce and M'Baku becomes the new ruler of Wakanda, now that Shuri has decided to protect their country as the Black Panther.