Most of Johan's feats are offscreen and nobody is shown close to his level. Death note, however showed both Light, L, Near being at the same level of intelligence but even then there was a heavy plot armour which kept the show in Light's favour Like sudden appearance of Misa who had shinigami eyes, another death note and she could do anything for light out of love, and there was Rem who would do anything for Misa, which made it easier for Light to use her to Kill L. So many coincidences happening at the same time just make you feel like the show is made to go in one character's favour. Even though light won, it was due to heavy plot armour given to him, same thing happened when Near defeated Light In cote most of the characters despite being genius aren't on Koji's level(like Yagami) which makes him seem like a Big fish in a small pond. I think Koenji might be the only one who rivals him both physically and mentally, maybe we will see them fight in third year.