What is the absolute highest rank in the US Army?

Pershing only had 4 Stars

General Bradley was considered for General of the Armies in the 60s, which would of implemented the official 6-star insignia. But, alas, as MacArthurs proposal fell through years prior, Bradley's proposal couldn't be agreed upon in Congress. It was dropped, and I don't think it's been spoken about since.

If Desert Storm had gone on General Schwarzkopf would have been given a 5th Star

SSG, the answer is General of the Armies, treated as a 6-star rank, but officially a 4 gold star rank. Held by two personnel, John Pershing (who created the insignia himself after Congress' approval) and posthumously George Washington, given that "no soldier should out-rank LTG Washington."

nah its my wife LOL

Correct myself! G Washington was promoted to General of the Armies also! George Washington died on December 14, 1799, at the age of 67. Upon his passing he was listed as a retired lieutenant general on the rolls of the US Army. Over the next 177 years, various officers surpassed Washington in rank, including most notably John J. Pershing, who was promoted to General of the Armies for his role in World War I. With effect from 4 July 1976, Washington was posthumously promoted to the same rank by authority of a congressional joint resolution.[141] The resolution stated that Washington's seniority had rank and precedence over all other grades of the Armed Forces, past or present, effectively making Washington the highest ranked U.S. officer of all time.

Ford promoted Washington to the rank of "General of the Armies of the United States," which is the official rank name Washington was given.