You are correct, Tuco (played by Eli Wallach) was "the ugly." Of course, Clint Eastwood as Blondie was "the good" while Lee Van Cleef as Angel Eyes was "the bad." I really enjoy this movie but my wife absolutely hates it. No point in even mentioning it on movie night since my wife will immediately veto it.
About forty years ago I saw a Clint Eastwood triple-feature at the drive-in: The Good, the Bad, & the Ugly; For a Fistful of Dollars; and For a Few Dollars More. Those were the days....
That’s a shame. Before she passed, my wife used to occasionally, for no reason whatsoever, just come out with woo-ee-woo-ee-woo,....DURANGO!