How do you beat the forest captain in the past in Pokemon ranger guardian signs?

Answer 1

That has no definite answer. However, I do recommend your partner to be Pidgeot (Sceptile mission) not only because it has high power and a type matchup but also beacuse its poke assist has a long range. This is very important for getting its bar to keep increasing even when Tangrowth uses its tricky "surround" attacks, practically making it impossible to loop. Keep Pisgeot ready (yes, it does have quite a long cooldown rate) and save it for times of dire need.

Additionally, I recommend grinding to the level above the recommended level, espiecially if it really was difficult enough for you to put it as a question here, and even more if you still can't pass.

Pidgeot gives a slate almost every time you catch it successfully but obviously would be hard to catch. I recommend saving the poke assist of a Sudowwodo for the times when it stops flying around like mad. Also, be aware of its Tornado it can form next to irself when it pauses. Use that time to grab Pidgeot with a poke assist (preferably with Sudowoodo as I mentioned above).