The Colonel was a character that appeared briefly in the Hellsing: Ultimate series. A foolish colonel who failed to realize that the men's loyalties lied with The Major, and made the mistake of incurring their wrath.
He is a tall, elder German officer with brownish-gray hair and an angular face. Due to his old age and decaying health, he uses a cane to aid his movement. The Colonel seems to be wearing a rather strange insignia on his uniform. While it's mostly that of a German Heer General, his collar tabs sport a combination of SS runes and an oak leaf used by an SS Standartenführer (Colonel), which is something that was never used by Nazis. This is likely due to producers and animators not doing proper research on Nazi uniforms.
From what little we see, he is arrogant and demanding. He is also shown to be violent when he attempts to beat The Major into submission.
After the events of Hellsing: The Dawn, most of the remaining Nazi officials escaped to South America sometime after the end of the war in Europe, taking with them a battalion of 1,000 Waffen-SS volunteers and a few members of the German Wehrmacht. They eventually formed the "Letzte Bataillon" a secret unit for the eventual execution of Hitlers Special Order #666.
As with most others outranking The Major, he falsely presumed that he was in control, when in fact, The Major was the one pulling the strings, and the one who had the soldiers loyalty.
In 1999, during the events of Hellsing's main storyline, they are shown to be more loyal to The Major than to the higher ranking Nazi officers. During the Major's return to Millennium's secret base in Jaburo, the Colonel became furious with the Major, frantically asking why the top echelons had never been converted into vampires and tried to beat him into submission. To this, the Major reveals two things: every single other member had already been converted, and the old generals themselves were the leaders only nominally. He then proceeded to assert his authority by ordering the soldiers to turn against their own superiors. Not long after, the Major had them executed on a live broadcast to the London summit between Iscariot and the Table, formally declaring war upon England. It's assumed the reason that the Colonel along with the other Nazi superiors weren't converted into vampires was so they wouldn't be able to stand in the way of The Major's plans against Hellsing and Alucard. This is likely due to the fact that the Colonel would've used the Letzes Battalion to establish a Fourth Reich, which the Major had no interest in. However, this was never stated in the anime.