'Hisuian Typhlosion is usually gentle and pacifistic. However, once angered, it loses control of its emotions and incinerates opponents until not even ashes remain.' - Legends Arceus website 

While Onibi may have become more open with other Pokemon since she evolved into a Typhlosion, she is also much more likely to express her anger much more ferociously if you cross her.... and while she absorbs the negative energy from the spirits of others and cleanses said energy, if she feels overwhelmed in any way, it can have literally explosive results.... 

Another old sketch I wanted to finish, I drew inspiration from the scene in Disney's Fox and the Hound where Todd and Copper became more feral for Onibi's stance and ferocious expression here.