This is some busy artwork!
The composition of characters is nice, and I especially like Omegamon partially hidden to the side, in his own space of sorts. You did a great job filling up the canvas with subjects, despite a number of them being traced/referenced. The shading on them is beautiful, and I really respect you for using traditional media! I especially like the sparing use of highlights. Tai's nonchalant laughter befits his character. (Nice touch on his shirt hanging out underneath his blue vest.)
The red and blue colour scheme for the background clashes quite badly, and hampers the impact. In some aspects, I get that this helps the piece stand out amongst many others in DeviantArt. It's a shame that your great paintings get lost in the stinging contrast — even if it was perhaps suppose to do the opposite, and help them pop out. Otherwise, the digital squares/pixels is a really cool touch! It fits in with Tri's special effects.
There is a good couple of Digimon Adventure Tai paintings composed with Agumon and his forms, but this still stands out amongst them in a striking and earnest way.