Overview

Despite its high defense, the sheer power of Ho-oh's best counters and its double-weakness to the highly pervasive Rock Type make it a manageable duo. It's not going to be easy, as it's going to take a team or two of powerful counters, but it's definitely doable, especially in Partly Cloudy weather. Prioritize Rock Types, and be aware of the fact that Solar Beam in particular is a huge threat.

Approach

Team composition

Rampardos can help get ahead of the clock due to its sky-high DPS

Shadow Tyranitar is the strongest overall choice, sporting high DPS and TDO.

Rock Wrecker Rhyperior is another fantastic overall choice, and it's basically a somewhat weaker Shadow Tyranitar in this raid.

Note on Hidden Power

Current discoveries by the community suggest that Hidden Power is always Fighting Type when used by a raid boss. This makes life fairly difficult for many of Ho-oh's counters.

Battling strategy

Re-entering is necessary; Solar Beam sets may need an extra re-entry

Note: "Good" movesets are not necessarily viable at the level indicated.