Here we report a dysprosium bis(amide)-alkene complex, 1-Dy, with the largest N-Dy-N angle yet observed for a formally two-coordinate Dy(III) complex. This gives rise to the largest magnetic anisotropy barrier for any compound of Ueff = 1843(11) cm -1 , and hence magnetic relaxation rates that are up to one hundred times slower than previous high-performance molecular magnets. Due to the far slower magnetisation dynamics of 1-Dy in the high-temperature regime, we find that magnetic hysteresis loops close more slowly and hence the coercive field is non-zero up to 100 K. On the other hand, 1-Dy shows much faster relaxation than other high-performance molecular magnets at lower temperatures, which state-of-the-art spin-dynamics calculations show arises from the larger spectral density for the low-energy phonon modes. The present work shows that there is still scope to increase magnetic anisotropy with more linear coordination geometries (e.g. > 150°) and more charge-dense ligands (e.g. dianions). If these features can be combined with rigid ligands that tend to reduced lowenergy spectral density and hence suppress two-phonon Raman relaxation (e.g. in substituted biscyclopentadienyl dysprosocenium complexes ), then molecular spin dynamics may be slowed across the whole temperature range. This may then deliver magnetic memory at even higher temperatures than seen for 1-Dy, providing multiple new pathways for future exploration.