Abstract: Core-collapse Supernovae (SNe), Long-duration Gamma-ray Bursts (GRBs) and exotic transients are exploding massive stars and constitute the most powerful explosions in the universe. Because they are visible over large cosmological distances, release elements heavier than Helium, and leave behind extreme remnants such as black holes, they are fascinating objects, as well as crucial tools for many areas of astrophysics. However, for many decades the fundamental question of which stellar systems give rise to which kinds of explosions has remained outstanding. I will discuss the exciting recent progress that we have made on this question in key areas by publishing and thoroughly analyzing the largest data sets in the world at the time and quickly following up mysterious exotic transients, as well as by developing radiative transfer methods to reconstruct the exploded star. I will conclude with an outlook on how the most promising venues of research - using the existing and upcoming innovative large time-domain surveys such as Zwicky Transient Facility and LSST - will shed new light on the diverse deaths of stars.