Unfortunately, Tarvos, the god of war, is at 6th place. Tbh, this is my favourite god, but too bad he is not suitable for my playstyle. These are reasons why i put him at the last place:
He is REALLY HARD to be pleased. You need to win battles to please him, but he is only slightly pleased by it. I once made a flawless no retreat run and i finally got his last perk at the end of lv7, this is the latest of all gods.
He is SUPER EASILY displeased. You mustn't retreat. If you are playing with spare life then yeah, it is kinda hard. But if you are playing Hardcore mode which has no life and extra tough enemies then it is NEARLY IMPOSSIBLE not to retreat.
Of course, he is only slightly pleased each time. Each retreat only slightly displease him, cuz he has sympathy. It will still be a huge pain though, i stuck at his 1st perk at lv7 once cuz i retreated 5 times
To rub salt in the wound, he has meh early buff. His 1st buff increases attack, cast and movement speed. Admittedly, this is good, but i never noticed the diference, propably cuz i don't pay attention to details.
Fortunately, he has AWESOME late game buffs. His 2nd buff improves fortitude, which is the resistant against powerful effects which are used by late game enemies. His last buff replaces your fallen teamates with Valkyries. Valkyries are only about lv7-8 but don't be fooled, they are far stronger than they look like.
It is such an unfortune that he has bad early game. While his 2nd buff protects you from dangerous insta-kills, his last buff grants you access to Valkyries who are really powerful, even against bosses. I never managed to get his last buff in Hardcore mode, however.