The Riddler has always tried to be a smart guy. His riddles have even gotten Batman confused at some points! Of course Sai doesn’t need to solve the riddles. He just needs to take Riddler down. That shouldn’t be too hard for someone like Sai. Sai has his speed and ninjutsu. Sai wins.
Sai may try to have skills, but in the end he’s just not strong enough to defeat her. Sakura has too much power. The Arc ends with this fight. Maybe Sai will be back one day, but I wouldn’t hold my breath for now. Sakura wins.
Kakashi has lightning blade. With it he can take out Sai pretty fast. Sai just doesn’t have the power to take on Kakashi. Sai can draw and use his abilities to try and take down Kakashi, but he will fail. Kakashi wins.
Sai lacks the skills to defeat Naruto. Naruto has his rasengan and with it he can blow away anyone. Sai doesn’t have the skills to dodge it or block it. He can try to block it, but he’d lose. Naruto wins.