Ok, to begin here, Breloom have quite the good things there. Toxic is one of the best status that a Pokemon can inflict, toxic will basically just keep getting stronger, no matter what, so Breloom can possibly do the wait game till toxic kill Orochi. Fake Tears might not seen so helpfull, considering his movepool, and Giga Drain normally stops after there is nothing more to leech of, however, Breloom can access Sludge Bomb, which is a much better attack in this situation, with Growth to boost Sludge Bomb's damage even more. Charm to reduce Orochi's offenses is also a nice thing. I don't know if we can consider Status stack, since that don't happens in the games, but that could be game mechanics. Drain Punch, Dynamic Punch and Focus Punch are goods moves to use when things get to CQC, but Dynamic have that poor accuracy and Focus Punch is too risk to be used here. However Drain Punch, Giga Drain and Leech Seed make a good heal combo in most battles.
However, with all that being saided, i don't see how Breloom will bypass that Regen, while Charm is good to lower his Physical strenght, Orochi uses more Range attacks than simple punches, and even with Fake Tears + Growth, that is not enough to bypass his regen, since he has the AP advantage. Even if Breloom could make all of his attacks weak, Orochi also have an attack that can destroy souls.
Orochi should take this via his Regen and Soul destruction alone