A climate crisis does not equate to 'end times.'
Directly, no. Indirectly through war, possibly. Indirectly through some of those who will die deciding to take their killers with them with a bioweapon, also possibly. We quite routinely synthesize DNA. We have synthesized a virus and demonstrated it worked. Smallpox was sequenced. Most DNA writing is done through big companies that are very careful about not producing known evils, but it doesn't have to be.
And with enough infection points smallpox would take us out. Doesn't even need to be made resistant to the vaccine.