TAR 21 and TAR 3 are the two best seasons of the show.
TAR 3 has a cast that is very likable except for Aaron and Arianne. The route is nearly perfect with visits to Mexico, Switzerland, and Vietnam. The only knock against the route is the single Moroccan leg where Andre and Damon get detained but otherwise it is a strong route. The elimination order could've been slightly better, but it's not enough to make me hate the season.
TAR 21 is similar to the season above except that it also has nice winners, whether they were deserving of it or not. Many of the teams this season are really likable except for Natalie and Nadiya, whom I found to be too "loud" for me. The route was really nice with the first being heavily focused on Bangladesh, China, and Indonesia. And the second half being focused on Russia, Spain, and France. The season has a lot of dark humor too and it also has the distinction of being one of the last "normal" seasons of the show before they started with the gimmicks after All-Stars. A+ season