What is the name of decepticon tank in transformers movie?

You're likely thinking of Devastator, the giant Decepticon construction vehicle formed by combining the Constructicons. He's one of the most iconic Decepticons, known for his immense size and power, and plays a significant role in the first Transformers movie.

However, it's worth noting that "Devastator" isn't technically a tank in the traditional sense. He's a combiner, a powerful robot formed by combining several smaller robots. While he does have a tank-like form, he's more accurately described as a construction vehicle.