Colress is the leader behind Team Plasma in the games Black 2 & White 2, after getting appointed the role by Ghetsis, where Colress' main goal is to discover the true way of drawing out the strength of pokemon. Honestly, I actually really love Colress' character design, with the researcher kind of look, as well as still appearing a little on the evil side of things, but again not my most favorite evil leader design. Now, I haven't played through Black 2 & White 2 in quite some time to fully remember how tough the fights were against Colress, but I believe they were a decent challenge compared to some other evil leader fights, and you fight Colress a few times throughout the games. The first battle, he'll use team of Magnemite & Klink. Second battle is at the Pokemon World Tournament, where he has team of Magneton, Elgyem & Klink. With the big final battle against Colress of him having team of Magneton, Metang, Beheeyem, Magnezone & Klinklang. Which that fight is most definitely the toughest Colress fight, with the Magneton having eviolite, Beheeyem & Klinklang having set up moves to boost their stats making them even more powerful hitters, magnezone having explosion + sturdy, then the Metang being able to boost its speed with agility with potential attack raises from meteor mash or flinches from rock slide. Overall, Colress is a great character, and I love how he in the Battle Tree in the Alolan games, but for a good time I honestly thought he was an admin and not an actual leader of Team Plasma, so that's why I ranked him here, because he just isn't as memorable as the other leaders that remain.
Ranks:
13th: Piers
12th: Chairman Rose
11th: Archer
10th: Lysandre
9th: N
8th: Colress
Leaders Left:
Giovanni
Maxie
Archie
Cyrus
Ghetsis
Guzma
Lusamine