The most likely location for an earthquake of high magnitude is at an Oceanic-Continental, Convergent Boundary.
At convergent boundaries, where an oceanic plate collides with a continental plate, one plate is typically forced beneath the other in a process known as subduction. This interaction can create significant stresses in the Earth's crust, often resulting in powerful earthquakes and volcanic activity. In contrast, while oceanic-oceanic boundaries can also produce earthquakes, the magnitude tends to be lower compared to the substantial geological activity associated with oceanic-continental convergent boundaries.
Transform boundaries can produce large earthquakes, but the locations may vary in magnitude and frequency compared to convergent boundaries. In summary, for high-magnitude earthquakes, the oceanic-continental, convergent boundary is the most likely location.