I suspect that when the boys in blue realized they were up against either Forrest or Anderson, the water flowed, if you know what I mean. But the two men were not the same. Both were hard men, but Forrest kept his humanity about him; Anderson became a mad dog killer. If you were a Union soldier and your only option was surrendering, you stood a better chance of living if you surrendered to Forrest. This wouldn't be true if you surrendered to Anderson. You would be killed, and maybe scalped.
Anderson had three younger sisters that were imprisoned in a jail in Kansas City. The jail collapsed killing one of his sisters, and wounding the other two, disabling one for life. This supposedely unhinged Anderson, and from that day on whenever he went into battle, he'd go in wild-eyed and frothing at the mouth. He supposedly kept a silk cord on his body and whenever he'd kill someone he'd add another knot to the cord. At Lawrence, (which happened shortly after the jail collapse), he added something like 13 or 14 knots. By the time he was killed in the fall of 1864, a silk cord was found on his body with over 50 knots on it.
I would love the meet a psychiatrist whose hobby was the study of Missouri guerrillas so I could better understand what was going on in the mind of some of these men. Did Anderson feel responsible for what happened to his sisters? And as the war went on, he became more vicious. I think He had become surrounded by so much killing and death that I don't think he expected to live though the war. I don't mean to say that he had a death wish, but I do think he was consumed with so much hate and revenge that he couldn't see an end to it, and death was his only way out.