I think Tom Baker faced an alien that fell on a vial of diseased material and the back of its head turned to jelly...
"The Android Invasion" which depicted the rhino-like Kraal (beating the Judoon by roughly 30 years) wearing Samurai inspired armor.
But there's also "The Seeds of Doom" (not to be confused with Patrick Troughton's "Seeds of Death") which contained some chilling sequences. To a certain degree there was the painful mutation of two different humans infused with Krynoid DNA. But far more disturbing was the compost processor of the main villain, Harrison Chase. It was basically a big a$$ wood chipper and Chase "fed" one person through it; tried to feed Sarah Jane until the Doctor managed to free her; and the Doctor and Chase struggled until the crazed tycoon got caught in it himself! True, we didn't actually see either victim shredded by the machine, nor did they have any blood splash against a wall, but it's quite obvious what happened.