Hello! My Raichu and I grew up together, we’ve been inseparable for many years. He and I love a good battle, and often train and participate in friendly fights. We do lots of traveling and my Raichu never backs down from any wild Pokemon if they try to attack. Recently we’ve been traveling into some mountains in Johto and i’m worried about Tyranitar. We take all the precautions residents recommended but my Raichu still insists on fighting. What can I do to convince him to back down?

Teach him Grass Knot.

Edit: I have just been informed by my editor that this does not, in fact, answer your question.

That having been said, as a native to the region myself, I can only guess what the locals have told you, but if they haven’t shared the most important thing to note, allow me to do so now. Tyranitar are extremely rare, as it’s necessary for them to control vast amounts of territory for themselves. Thus, they make their homes in more hostile areas, and they’re generally more interested in battling each other than a raichu that has no interest in claiming their mountains as its own. Discouraging your raichu from finding and battling them may be a simple matter of not venturing too deeply into the Johtonian mountains.

Should you encounter one anyway, inform him that you won’t give him commands throughout the battle. Your raichu will then have two choices: fight the land dragon made of rock himself or listen to reason and follow you away. If he chooses the former option or if the tyranitar notices you first, then it may be too late to deescalate the battle. One hit will alert the tyranitar to your location, which in turn will incite the tyranitar to attack. Your only choice at that point would be to follow through with the battle, so keep your raichu’s poké ball and at least one water- or one grass-type on hand—preferably a grass-type that knows Spore. Recall your raichu and have the grass-type disable the tyranitar, then get a head start on running before your raichu breaks free. 

In all other instances (that is, if you haven’t encountered a tyranitar at all), remind your raichu that if a dangerous situation arises (such as a tyranitar encounter), your safety should mean more to him than the battle. While he may be confident in his ability to keep himself safe, with a pokémon as powerful as tyranitar, there is no guarantee for you. Word it politely, of course, but be sure to get that point across. If your raichu is loyal to you, it should at least be food for thought—or an opportunity to open up some form of conversation (or, well, the closest thing one can have with a pokémon) with him.

Good luck, anonymous, and may your journey be exciting!