It means ‘I do not wish you any harm’ Though not considered grammatically correct, the two negatives reinforce each other here, not cancel each other out.

ヤッホー！ “I do not wish you no harm.” This is similar to a formal way to say, 「お気をつけて」。 But is this the right sentence? This is considered a “double negative” sentence which turns into a positive sentence. For this sentence “I do not wish” is like saying I I am not hoping or I am not praying. “…no harm” is saying that nothing with hurt you or cause any problems. Saying “I do not wish you no harm” is saying I wish you harm because it’s a double negative. I don’t know the song’s lyrics but I think this should be said like this. “I wish you no harm.” This is telling the person that you wish, hope, pray that nothing bad happens them. This is a good expression. This is a positive sentence. The other one was a double negative and therefore makes it a positive. “I DO NOT wish you NO harm.” I hope this makes sense. 頑張ってね！*\(^o^)/*

Mmm, I think that means I know you harm