The Energon Pub

I think sound wave would send his ho's (his cassette's) and sick them on him and then sound wave would beat him up thats what i think

Ultra Magnus.

Firstly, you only stated Soundwave, not "Soundwave and his minions".

We know Soundwave is a mind-reader. Judging by Magnus' EM abilities and those big antennae, maybe he's a mind-reader too and he keeps quiet about it because it's a critical advantage?

Soundwave is clearly smaller, weaker and slower. He can shrink and hide in cassette player mode but Magnus can detect him. It's possible that Soundwave could sneak himself inside Magnus and then expand, bursting a big hole in Magnus. This would be especially true if Soundwave is picked up by a human, who is then given a lift by Magnus.

Magnus will probably win but Soundwave has plenty of information about Autobot strengths and weaknesses. He could target key components in Magnus' body, doing minor or even major damage.

If Magnus has Soundwave at his mercy, Soundwave could trade vital secrets for his life. If these secrets are fake and misleading, Magnus might find himself in danger later. This could be a delayed victory for Soundwave. However, if my Magnus telepathy theory is correct, Soundwave would be denied his victory.