"I'd better get this one out of the way before the game mechanics change" edition.
"eve how long does it take for supercarrier to kill carrier"
About 100 seconds... assuming no lag, rainbow bomber damage and that the carrier is not running a local rep.
The longer version is that a carrier has about a million hit points, and a nyx does about 10,000 damage per second. A carrier can generally rep a thousand or so damage per second; however, a triage carrier set up for local rep can rep a lot more, usually enough to tank one supercarrier.
"what does it take to take down a carrier in eve?"
See above. Carriers have a million hitpoints and can rep 1-3k dps, or up to 20-30k while in triage. If you can find a solo carrier, you can probably get away with logi and a couple battleships with neuts fit.
"eve naglfar what is it used for"
"eve can doomsday miss"
Yes. Sort of. More precisely, it is possible to prevent a doomsday which is activated on you from landing.
When a doomsday is fired, it takes about 30 seconds to land. If you have effects on you can see the doomsday effect hitting your ship shortly before the damage is applied, and have a few seconds to GTFO. If you manage to get off-grid, it effectively "misses."
It is possible that if a doomsday was activated on you the titan would start redboxing without there being a guns hit/missed notification. I can't confirm this, as it's understandably difficult to test, but if true it may be possible to use a titan overview to detect incoming doomsdays.
When titans are used against subcapitals, logistics, T3, fleet boosters and expensive ships (e.g. machariels) are prime doomsday targets, so their pilots try to detect doomsdays being activated on them and warp out when it happens, resulting in the doomsdays being wasted. T3 in particular can use interdiction nullifiers to make themselves immune to bubbles, and I believe this has been used as a tactic wherein nullified friendly T3 are deliberately bubbled to bait enemy titans into wasting doomsdays.
If you're in a capital, jumping out works too -- once the jump command goes through, you're safe. I once jumped my nyx out with 17% armor left and three doomsdays running on me, which would have killed me if they had landed.