Red, Yellow, Emerald, Lance and Giovanni from the Pokemon Adventures, I can't really decide on one, they are all too awesome! Red is really adept at battling and has won against other strong trainers even at a disadvantage, like beating Blue with a team a good 10 levels or more lower or Bruno using only his Eevee! Yellow because being able to hear the hearts of Pokemon and heal them with a mere touch is really awesome, on top of being a strong battler too and, well, she's way too moe to ignore! Emerald because he basically invented the "Ultimate strategy" for competitive battling (even though no one uses that anymore), beating the entire Battle Frontier, he has some funny quirks and, last but not least, his
real body looks HILARIOUS!
Next up we got Lance, who, on top of having the same special powers Yellow does, is the leader of the Kanto Elite 4, a brilliant strategist, unbelievably powerful when battling and has a really cool design! Finally, we got the real star, Giovanni! We all know him, some hate him, some don't, but that doesn't change the fact that he is BY FAR the strongest trainer in the entire series, being able to keep in check even two legendaries at once with a single Pokemon, has only lost 3 times as a Gym Leader, has an entire criminal organization under his command, has controlled Pokemon like Deoxys and (temporary) Mewtwo, got the best poker face anyone could have, has impressive physical abilities being able to move faster than even Red and LITERALLY tries to kill all those who challenge his Gym!
As for the anime, the only character I like is Silver, mostly because we know almost nothing about him and he is almost certainly Ash's runaway father!
As for the games, I think I'll choose Red from the second and fourth generations, mostly because I like the battle music when battling him and he has a really good team (besides a Pikachu that can't even beat a same level Gyarados)!