Shalba harbored an immense hatred for Issei after he defeated him in his Juggernaut Drive. Issei also disliked Shalba for his past actions towards Asia. Because of Shalba's growing insanity and his viewing Ophis as merely a tool to raise his own power, Issei's hatred towards him only grows stronger and expressed complete disdain for Shalba's delusional ambition for world domination. When Shalba viewed the world that had rejected him and tries to destroy the underworld using Bandersnatch and Jabberwocky, Issei recognizes that he has basically gone insane and outright kills him to save Ophis. This would make Shalba the first person Issei himself has ever actually killed. Ironically Shalba managed to use Samael's poison to finish Issei off as well but, unfortunately for Shalba, Issei's soul survived despite his body being destroyed and would later receive a new body.
Shalba appeared to possess an intense rivalry with Vali, as suggested he utterly despised Vali for being a human hybrid as well as thwarting his ambition for world domination through his cursing of Vali when he witnessed Issei using Albion's power against him in his Juggernaut Drive state and again in Volume 11 when he cursed for both Vali and Issei for thwarting his ambition for glory.
Shalba despised Sirzechs believing that he is superior to him due to his heritage. He also views crimson as an ominous color.
Shalba was using Diodora as a pawn in his plan. He later killed Diodora for foolishly using Ophis' snake during his match against Seekvaira, as a result for his plans being nearly predicted and easily being defeated by Issei, considering him useless.