However, Powell was a RINO (Republican In Name Only)as asserted by Trump.
Colin Powell was a military officer who joined the army in 1958 and completed his military training in Georgia where he was refused service in restaurants and other public facilities. Still, he dedicated his life to the service of his country.
Following service in Vietnam, he served a White House Fellowship under Richard Nixon from 1972-73. He then earned an MBA and attended the National War College. He served as a brigade and corps commander.
During the Reagan administration he served as senior military assistant to the Secretary of Defense and Deputy National Security Advisor. Ronald Reagan appointed him as his National Security Advisor in 1987. George H. W. Bush appointed him as Chairman of the Joint Chiefs of Staff in 1989, the most senior and highest ranking military officer in the United States. After serving in that role and overseeing the 1991 Persian Gulf War, he retired in 1993. He was awarded both the Congressional Gold Medal and Presidential Medal of Freedom in 1991 and a second Presidential Medal of Freedom with Distinction upon his retirement from the Army in 1993. His military service won him admiration among both Republicans and Democrats.
During his 35-years of military service he was an independent with no declared party affiliation or registration. He declared himself as a Republican in 1995 and began campaigning on behalf of Republican candidates that year. Given his widespread popularity among Republican and Democratic voters, there were intense efforts made to convince him to run as a Republican candidate for president in 1996, Powell declined to run saying that he lacked the passion for politics needed to be a successful candidate and president. Despite his decision not to run, he won the 1996 New Hampshire Republican vice-presidential primary on write-in votes.
George W. Bush appointed him as United States Secretary of State in 2001. He retired from public service in 2005.
As for your embrace of sociopath and malignant narcissist Trump's description of Powell as a RINO, I'm not the least surprised. Colin Powell was a centrist and a moderate in a Republican Party which has taken a dangerous turn to undemocratic radicalism which indulges a cultish personality worship and fear of Trump and has actively sought to push out, attack, or denigrate anyone in the party that doesn't robotically tow that line.