Debut Episodes of Rival Characters in Detective Conan (Case Closed)?
Notable characters

Kaitou Kid
Heiji Hattori
Subaru Okiya/Shuichi Akai
Rei Furuya/Bourbon
Makoto Kyougaku
Masumi Sera
Eisuke Hondou
Haibara Ai/Shiho Miyano
Kazuha Toyama(Hattori Heiji's Love Interest)
Black Organization(First,Second and Third in command-Third one is Gin and you should check the members)
Maybe also check Ran's Mom and Kudo's Mom's rivalry,Kudo's father and Kid's father's rivalry

From Magic Kaitou-
Aoko Nakamori(Kaitou Kid's Love Interest)
Ginzo Nakamori
Akako Koizumi
Saguru Hakuba

From Yaiba-
Yaiba Kurogane
Soshi Okita

Also a crossover with Lupin the third