The electronic system is driven far from its ground state in many applications today: attosecond control and manipulation of electron dynamics and the consequent ion dynamics, photovoltaic design, photoinduced processes in general. Time-dependent density functional theory is a good candidate by which to computationally study such problems. Although it has had much success in the linear response regime for calculations of excitation spectra and response, its reliability in the fully non-perturbative regime is less clear even though it is increasingly used. In the first part of the talk, I will show some of our recent work exploring exact features of the time-dependent exchange-correlation potential that are necessary to yield accurate dynamics and discuss approaches to develop new functionals going beyond the adiabatic approximation. In the second part of the talk, I broaden the focus to the description of coupled electron-ion motion. When the coupling to quantum nuclear dynamics is accounted for, we find additional terms in the potential acting on the electronic subsystem, that fully account for electron-nuclear correlation, and that can yield significant differences to the traditional potentials used when computing coupled electron-ion dynamics.