He was sued by Harlan Ellison, who is a major league PIA in his on right, for plagiarism. Ellison claims Cameron lifted the plot for Terminator from an Ellison screenplay on “The Outer Limits”.
They settled and Ellison got credit on at least the home release of the Terminator. The rest of the settlement seems to be behind a NDA. Cameron denies everything but he did settle.
I generally like Ellison's work but the man was a bit of a nutcase. He was the grumpy old man of science fiction. The slightest resemblance to any of his work meant almost automatic litigation from him.
Want to know how twisted Ellison was? Go find the original draft of "The City on the Edge of Forever", it's WELL worth reading.