Which group of poets reacted against the genre of realism?

symbolists.

Explanation:

Following Baudelaire´s decadent movement, many were influenced by his writing, but perhaps it was Mallarmé who felt this influence the most and who took it further and managed to create a coherent literary movement called symbolism, which grouped together several memorable poets like Verlaine, Rimbaud, Valery, amongst many others. Symbolists reacted against the sobriety of realism and their pretension to capture the essence of reality through detailed and profound descriptions, instead focusing on limit experiences to explore the real nature of the mind in its correlation with reality.