Story: Avengers, vol 1, #62
Background: T'challa returns to Wakanda with the Avengers, after leaving his friend M'baku to play Chieftain in his absence. However, M'baku wanted Wakanda to himself and thus... fisticuffs must be had! M'baku drugs T'challa and the Avengers and reveals his true self to T'challa....
[Scan Tip: Click to enlarge the images and they are easier to read. You can scroll through them all that was as well. --- Shadow]
On a side note, this is the earliest Tribal Challenge I can remember in the books, but I am not 100%.
And there we get the full account of M'baku's treachery. He wants to return Wakanda to its pre-technological state. This book was obviously made before the Hudlin ret-con that Wakanda has always been advanced.
Yeah... M'baku basically crushes himself trying to knock down a statue. Not his finest moment, that is for sure.