Shinobu Kajita

When Shinobu first appeared, he appeared to be a quiet and shy kid. After revealing his true colors, he is ultimately revealed simply as a brat. He sees Vanguard as a way to prove how strong he is. He deems that only the strong can survive in this world. However, it is seen that he panics quite easily, some examples can be when he's about to lose against Megumi Okura and Yu-yu Kondo. Tohya Ebata and Megumi even commented on the fact that he acts somewhat as his avatar, Avaricious Demonic Dragon, Greedon.

(Source: Cardfight!! Vanguard Wiki)