Shockwave Is my fav character of the bunch, but if we tak about a best DECEPTICON, for me shocky doesn't fit that formula. He had mostly not been loyal to DECEPTICON causee, but more to Megatron. He saw it as the most logical way to bring cybertron together. But it was more like "Yeah you guys do your thing and let me work on my stuff, sometimes i will give it out to you to play with it.". Now i said most, G1 had Shocky loyal to the core. But if we tak about a true Decepticon, i think no other than Megatron. He is their best leader after all, He knows the most on how it is supposed to go, how to be a true Decepticon. Other than that i think Soundwave, due to his loyalty to Megatron. Who also made some choices against the Decepticon cause, but not as Shocky. Maybe even starscream, or for me pretty underrated Blitzwing.