This is a complex sentence.
"he would have crucified us all" - this is the main or independent clause
"if he had lived" - it is the subordinate or dependent clause. It cannot form a sentence by itself. It needs the main clause to make sense.
The subordinate clause is here a conditional clause. It gives the condition for the action in the main clause to happen. "Crucification" can happen only if someone "lives". So it is a conditional adverbial clause.
The sentence describes an unreal situation in the past. "he did not live". Hence "he could not crucify us".