Depends on context but most likely Slippery Slope fallacy or Straw Man fallacy.
As explained pretty well by Purdue University Online Writing Lab:
"[The Slippery Slope fallacy] is a conclusion based on the premise that if A happens, then eventually through a series of small steps, through B, C,..., X, Y, Z will happen, too, basically equating A and Z. So, if we don't want Z to occur, A must not be allowed to occur either."
Also explained by Purdue:
"[The Straw Man fallacy is when] the author attributes the worst possible motive to an opponent's position. In reality, however, the opposition probably has more complex and sympathetic arguments to support their point. By not addressing those arguments, the author is not treating the opposition with respect or refuting their position."