Frank Castle aka the Punisher is known for being a brutal street-level vigilante who deals out deadly punishment upon those who commit criminal acts of a certain degree in his city, so when he was turned into an angel, he suffered a massive blow to his character. Not only was that incarnation of the Punisher not well received by fans in the slightest (with the run only being four issues long), the Punisher himself knew his time as an angel was a huge mistake.
Frank Castle became the Punisher after his wife and children were murdered during a gang related shoot-out in the park. While that traumatic event caused him to cross the line and become a full-on murderous vigilante, Frank had the itch to become the Punisher within him throughout his entire life and made efforts to prepare for a day where that internal itch could eventually be scratched. As a young man, Castle joined the U.S. Military where he eventually became a captain in the marines. His military service taught him everything he knows about wartime tactics, weaponry, and fighting styles. Basically, the Punisher built himself into the antihero he is today, something that separated him from some other Marvel characters who wield magic or were granted superhuman abilities.
In Punisher Vol. 4 by Christopher Golden, Tom Sniegoski, and Bernie Wrightson, the Punisher is granted angelic powers as the angels of heaven needed a warrior on Earth who would rid the world of the evil that plagues it. The angels get Punisher to agree to this by telling him that his family, after they were killed, went to heaven and the only way he would become worthy of entering the pearly gates himself and see them again (even after committing countless murders) is by becoming an angelic force for heaven. From that point on, every murder the Punisher committed cleansed his soul rather than stained it, and he was committed to going above and beyond so that he could see his family again. That is, until he decided to abruptly quit by the very next run for reasons that were blatantly obvious to readers and, evidently, even more so to the Punisher himself.
In Punisher Vol. 5 #1 by Garth Ennis and Steve Dillon, the Punisher is back to his classic self, killing drug dealers and gang members with no one to answer to but his own demented justifications. While killing a high-level mobster, the Punisher addresses his time working for heaven, and merely says that he didn’t like it, so he stopped, with no further explanation given. The hilarious part of it was, that was all the explanation anyone wanted. Making the Punisher an angelic, mystical hero was a mistake and no one wanted to dwell on an entire storyline where he leaves the angels and goes back to his old ways. Fans and the Punisher knew it wasn’t great, and decided to unceremoniously leave that storyline back in Volume 4 where it evidently belonged.
When Punisher was granted the grace of the angels, he lost his uniqueness and became just another superpowered character fighting evil with the help of a mystical force. While it didn’t resonate with fans, Punisher Vol. 4 was undoubtedly a creative change-up for a character who pretty much just goes around and kills criminals, but it also stripped him of everything that made him the Punisher as it betrayed his established character and replaced it with an otherworldly force that turned him into another supernatural antihero akin to Ghost Rider. For that reason, even the Punisher knew his time as an angel was a mistake as he basically says as much in the very next story arc.