What are the fight scenes that stand out for you as the most memorable and impressive?
Two I can think of offhand for openers are...
the Thing vs. Silver Surfer in FANTASTIC FOUR 55 by Lee, Kirby and Sinnott.
and
Another that stands out for me is across several issues of the NEW GODS by Kirby, in issues 5 and 6 (facing the Deep Six, starting with a splash page where you just see a full page showing the empty harness for the Deep Six's giant monster, then next issue see it in action sinking ships on the ocean, and then a clash of Orion and Lightray against the Apokalips gods of the Deep Six.)
Then issue 7, "The Pact" (showing the initial war of the New Gods, with the origins of Isaiah/Highfather, Darkseid, Orion and Scott Free, with some great scenes of inner conflict as well as scenes of war.
And issue 8, with Orion vs. Kalibak, in "The Death Wish of Terrible Turpin", Turpin being a police detective who is way out of his league but in gutsiness that gains admiration of the gods, still tries to arrest Orion and Kalibak. In some ways similar to FF 55, where they wreck half the city slugging it out. A battle that continues in NEW GODS 11, and unfortunately the series was cancelled after that, and we never saw the follow-up Orion vs. Darseid "final battle" that was built up to. At least not to my satisfaction.
Those are a few of my favorites, what are some of yours?