  Long duration gamma-ray bursts (GRBs) are powerful cosmic explosions,
signaling the death of massive stars. Among them, GRB 221009A is by far the
brightest burst ever observed. Due to its enormous energy
($E_\textrm{iso}\!\approx$10$^{55}$ erg) and proximity ($z\!\approx$0.15), GRB
221009A is an exceptionally rare event that pushes the limits of our theories.
We present multi-wavelength observations covering the first three months of its
afterglow evolution. The X-ray brightness decays as a power-law with slope
$\approx\!t^{-1.66}$, which is not consistent with standard predictions for
jetted emission. We attribute this behavior to a shallow energy profile of the
relativistic jet. A similar trend is observed in other energetic GRBs,
suggesting that the most extreme explosions may be powered by structured jets
launched by a common central engine.
