I personally could never fear death itself as I believe death to just be the absence of everything, the thought of a permanent and dreamless sleep comforts me so much, what I fear instead is existence as it's the ultimate cause of all harm and suffering, but without existence one cannot suffer.
But when it comes to actually going through with suicide then I imagine that those who succeeded had access to a method that they felt confident in and they just got so determined to leave which allowed them to overcome the SI, I envy those people as suicide really just isn't straightforward at all, it's like the SI exists to prolong suffering.