Oxford University's Future of Humanity Institute identifies 12 major existential threats to humanity. While it's easy to see that the list is a good compilation of overall mishaps, the type and probability of each event is poorly understood - sometimes due to the nature of public discourse and other times because we simply don't have any prior data on complete unknowns.
Extreme Climate Change
Probability: certain within the next century
Impact: Poorer countries will bear the brunt of the impact, but there will also be global disruptions and sustained supply chain collapse. This is a threat to already stressed local and global economic systems. Systemic effects will result in mass casualties, further rise of extreme political and religious systems, a prolonged stagnation of scientific and intellectual output, a temporary halt to medical advances and reduced capability for medical intervention in general, and will likely delay an interplanetary expansion of our civilization by more than a century.
Threat range: narrow. While the systemic effects are not entirely predictable, the nature and scope of the threat is understood.
Result: developmental delay. While this threat will kill a lot of people both directly through its effects and indirectly through the inhibition of scientific and technological progress, it is not a likely threat to our civilization in the long term. The event is exceedingly unlikely to eliminate the human race or all life on the planet.
Probability: multiple instances of varying certainty within the next century.
Impact: ecological catastrophes are a catch-all category for any severe change to the Earth's ecosystem or its parts. For example, climate change is certain to trigger several of these. The effects are expected to cover a wide range, from no discernable impact on human life, to mass casualty events.
Threat range: intermediate. Unforeseen scenarios are likely to happen. Advance warning windows range from months to centuries, with varying options for intervention.
Result: developmental delay. For this to eliminate all human life, the biosphere would have to be destroyed completely, and humanity would have to be unable to maintain isolated environments where life can still persist.
Probability: improbable within the next century
Impact: a supervolcano eruption would trigger an immediate climate desaster. The eruption itself would be a mass casualty event, followed by a temporary collapse of global food production.
Threat range: narrow. The threat is well defined and understood. Advance warning will likely be measured in days or less. Options for intervention are extremely limited.
Result: developmental delay. A supervolcano eruption will not eliminate our civilization or the human race.
Probability: limited nuclear exchange likely within next centure, full arsenal exchange unlikely