The Perils of Protection
"And I. Am. Iron Man." He gave just a moment more to the thought of his loved ones, wishing them a long and happy life. For Pepper to be strong, for Rhodey to not give up, for Happy to take care of them, for Harley and Peter to learn and for Morgan to grow. Knowing that they will still have each other made leaving them just a little easier. Keeping in mind the thought of safety and protection, he snapped his fingers, forcing the energy that was tearing through his body to tear down the ones that were threatening them instead. The pain was an old friend at that point. He had endured the arc reactor in his chest, the palladium poisoning, countless beatings and watching the ones he cared about die or get hurt because of him for less, and now when he could use it to save them all, it was almost a relief. For a moment the burning sensation receded to his hand, but when it started traveling up his arm again, his elbow exploded with pain.
It was a peculiar sight. Thanos and his army were collapsing to dust, Tony let out a scream, and everyone was staring in dumbfounded shock at Loki, who hefted a giant bloody sword over his shoulder, pointed at the burnt, shriveled and smoking arm on the ground and cheerily said: "You're welcome!"
(Of course, after that he heals the stump so that Tony doesn't die from blood loss, though the lower arm couldn't be regrown due to the influence of the Infinity Stones. Tony doesn't seem to mind too much, as evidenced by his many gleeful jokes of "being stumped".)