The President's power to veto legislation keeps can prevent the House and Senate from passing unconstitutional legislation. Congress has the power to over-ride a Presidential veto with a vote from two thirds of the House.
If Congress does not hold the President accountable, they are an accomplice to his crimes. When they allow him to violate the Constitution they collectively violate the oath they took to preserve, protect and defend the Constitution.
The Constitution states that the President is the Commander-in-Chief when he is called into service by Congress. This was a safeguard to prevent the President from abusing the power of his office. When President Trump authorized the air strike in Syria he had to violate the Constitution. When a President does whatever he wants, he becomes military dictator. Congress must collectively put their foot down and prevent the abuse of power by the President.
Members of Congress are representatives of the people and must obey the Constitution and hold the President accountable. When the President attacked Syria he put the lives of the American people at risk without the consent of Congress. In my opinion this was an act of treason and we need a Congress that will limit the power of the President to the provisions in Article II of the Constitution.
I believe the President should be held accountable if he continues to abuse the powers granted to him in the Constitution. The ultimate power of Congress is to impeach the President and I believe the people have delegated their power to 435 representatives who are partners in his crimes.
A king, dictator or emperor has the power to wage war at his own discretion, but a President does not.