Lt. Sulfurch is an Utrom (a brain like alien from another Dimension) under the employ of the ruthless Utrom commander, General Krang.  Utroms in our series have varying delivery styles (many great examples can be found in this episode: https://www.youtube.com/watch?v=1rhRBGIZh0s) and while most take inspiration from Krang and various Utroms as presented in TMNT media over the years, I'm quite open to your interpretation.  Because they're so odd, Utroms offer a chance to get creative so please feel free to experiment with your voice and submit several takes if you'd like.  Just remember that no matter  what sound you go with, keep the delivery grounded - this is not a comedic role.