The Gorn
Strange New Worlds may have mucked up canon a bit with The Gorn being so heavily used. After all, the original series did suggest (if not outright state) that The Gorn were a fairly mysterious race of aliens who had never been seen before by human eyes. Yet, this was James T. Kirk's perception and it's quite possible he had never heard of any encounter with the race.
Also, to take the heat off of Strange New Worlds, another prequel show also broke continuity. Enterprise featured The Gorn in an episode and it's set far before Strange New Worlds.
Yet, if you can look past the fact that Kirk doesn't know much about The Gorn despite all that we've seen from Strange New Worlds, you end up seeing how much better they are as an alien race now. Strange New Worlds made them unforgivable. They're unrelenting. They're monsters who exist to feast and breed, using the bodies of unsuspecting aliens to do both.
The depths that these aliens were given truly exceed anything that the original series gave us. So while it's still a battle with a rubber-suited man, the Kirk and Gorn conflict now has so much more weight to it. Especially when you consider what the Gorn will do to Kirk if Kirk loses.