Yato vs. Rabo.
This battle was all out amazing!
After Hiyori's memories cracked, Yato became just exactly what you would expect; his old, angry merciless self. However, Yato seemed to be laid back the entire time as if he were holding all of his powers back.
The season finale of Noragami, which featured this insane rage moment, had a bunch of hidden messages within it that you may have not noticed.
1. The entire first season has hinted back to Yato's former self in a time where he was supposedly a merciless God of Calamity. Although, it would seem impossible at first glance due to his aloof behavior. No one would have believed it until his past spun out in front of him in place of Hiyori. It's the moment we were all waiting for; what is Yato really like? We saw a merciless God, exactly as it was explained.
2. Despite the fact that this battle brought out the worst in Yato, it also demonstrated the best in him. It clearly showed the deep devotion he has to his friends and family, them being Hiyori and Yukine.
3. Yato was filled with a slight depression, but more like pity for Rabo. After all, they were partners for a very long time in the past, fighting back to back. He probably felt mixed feeling of immense hatred as well as the feeling of reliving his entire past with Rabo as he braced to end him. Still, there was no sign of hesitation. If you mess with the ones he cares for, you will regret it.
"No. You come to me. I'll hack that grin off your face."