1) permafrost melt, albedo feedbacks, etc., which has been considered in the most recent IPCC reports and is still being researched
2) sudden mass extinction due to biodiversity loss
As far as 1) goes, read the IPCC report and get back to me. 2) is scarier, for sure, but there is not enough research done to conclude that we have breached or are about to breach an extinction tipping point. Some recent models suggest phytoplankton extinction (the usual tipping point in doomer arguments) may be reversed in lower latitudes in a warming climate. But no one knows.
“Many of those making facile comparisons between the current situation and past mass extinctions don’t have a clue about the difference in the nature of the data, much less how truly awful the mass extinctions recorded in the marine fossil record actually were,” he wrote me in an email. “It is absolutely critical to recognize that I am NOT claiming that humans haven’t done great damage to marine and terrestrial [ecosystems], nor that many extinctions have not occurred and more will certainly occur in the near future. But I do think that as scientists we have a responsibility to be accurate about such comparisons." https://www.theatlantic.com/science/archive/2017/06/the-ends...