Shadow Regigigas

The sheer power of the Shadow boost combined with Regigigas' raw strength has an interesting effect on the progenitor of the legendary titans. While its attacks aren't great and generally won't work well even when on-type, Shadow Regigigas can actually be a decent generalist. In terms of neutral damage, it's actually fairly high on the list, hitting harder than the majority of the game's attackers. It's to the point where Shadow Regigigas can be a useful attacker for newer players, as it can slot into a lot of raids and still hit really hard.

However, we can't really recommend doing this. While Shadow Regigigas hits hard on the neutral scale, there are still quite a few powerful Pokemon that out-class it on said scale while still showing up for even better performance when on-type. On top of that, the "neutral damage scale" isn't really a useful metric to begin with, as adding any type-weakness at all causes Shadow Regigigas to realistically drop way down the list. For these reasons, we can say that it's not the worst Pokemon for raids, and may find generalist utility for some newer players, but it's really not worth making an investment in.

Best PvE Offensive Moveset

• Hidden Power is more useful than Zen Headbutt as long as a relevant typing can be obtained. 
• Giga Impact is very powerful with STAB, and will tend to outperform other charge moves as long as it's not resisted (not factoring weather). 
• Focus Blast offers wide coverage, and could synergize with certain Hidden Power typings, but maybe consider an actual Fighting-type Pokemon instead. 
• Thunder is an inferior option, consider an Electric-type Pokemon instead.