I tried soloing a Impossible raid battle. I gotten around 200,000 honors. I still need 43% of health to go, with 22 minutes remaining. It was definitely long and hard. True power with multi-/wave charges did me in.
Anyways, judging from my analysis, I believe that you can top a 300,000 honors if you can manage to solo the fight all the way through.
Maybe, there's a honors formula ratio between the solo and raid battles.
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I then tried soloing a Extreme raid battle. I defeated Geo, and topped up around 70,000 ~ 80,000 honors. Much more manageable, but still fairly difficult. Near death experiences do occur. The honors count is not exactly cropped, but still, it's quite the fraction gain compared to Impossible raid battle.