[XorNot]

James Webb is the one I worry about the most. ITER has a taken a long time, but they're making steady forward progress with it.

Whereas I live in fear that James Webb will suffer a failure during launch or deployment that just turns it into a very expensive explosion.

[aylmao]

I agree. Or even if nothing explodes, I'm worried that during the unfolding something will break or get stuck and, and unlike Hubble it won't be "easily" repairable (if at all). Hopefully this doesn't happen, because it is a once-in-many-decades project.