  We study black hole extremality in nonlinear electrodynamics motivated by the
Weak Gravity Conjecture (WGC) and the Festina Lente (FL) bound. For
illustration, we consider the Euler-Heisenberg model and the Dirac-Born-Infeld
model in asymptotically flat spacetime, de Sitter spacetime, and anti-de Sitter
spacetime. We find that in all cases the extremal condition enjoys a certain
monotonicity expected by the WGC. This provides evidence for the conjecture
beyond the leading order corrections to the Einstein-Maxwell theory. We also
study how light charged particles modify the mass-charge relation of Nariai
black holes in de Sitter spacetime and discuss possible implications for the FL
bound. Besides, we point out an interesting similarity between our black hole
analysis and gravitational positivity bounds on scattering amplitudes.
