X-Men (1963) #127
"The Quality of Hatred!" is written by Chris Claremont and drawn by John Byrne and Terry Austin. Proteus, Weapon X, is the most dangerous mutant alive imbued with the power to warp reality to his every whim. He needs fresh bodies every few minutes for his energy form to inhabit and the human hosts burn out quickly. The X-Men have come to Scotland to rein him in but have been finding merely a trail of mummified bodies to mark Proteus' passing. However, just last issue Wolverine, Nightcrawler and Storm came across the murderous mutant much to their regret. With Logan and Kurt still reeling from Proteus' last blast of bendable physics, it's up to Storm to try to slow him down. But even hurricane-force winds aren't enough to hold him back. Only sniper fire from a nearby ridge (courtesy of Weapon X's mother Moira MacTaggert), is able to keep the reality-warping assailant at bay. But before Moira can complete her task and assassinate her son, Cyclops intervenes.
In fact, it's Cyclops--acting a true team leader--who challenges the entire team to keep their heads while hunting Proteus. In order to ensure his team is battle-worthy, Cyclops has to take on Wolverine, Nightcrawler and Storm. Each pass with flying colors. Meanwhile, Mutant X is making his way to Edinburgh to the home of his father, Joe MacTaggert. Blaming his politician father for abandoning him as an infant, Weapon X moves in for revenge. Possessing the shell of his own father, Proteus feels energized. Will the X-Men be able to stop the madman mutant before he kills his own mother?