This isn't so much a character as it its the ability (or lack-thereof) of the Digimon. Why do you think Agumon and Gabumon got to warp-digivolve and all the other Digimon didn't when they were reaching the same level of digivolution? It was something I noticed when watching the Apocalymon episode.
Time constraints. I think the writers really, really wanted to have all the digimon reach ultimate level, but given that each evolution would have required its own episode they just had to drop it in order to tie up the loose ends with all their villains. If I’m remembering correctly, at least a few of the other Adventure digimon besides Agumon and Gabumon did hit their ultimate evolutions in video games/movies/other supplemental material, just not in the anime.