Short answer: No, not if you mean “all life”, nowhere near. There is nothing that can do that in the current solar system for millions of years into the future. It will of course kill some life. It would have major local effects over a region up to several hundred kilometers from the point of impact, if it landed on land. If landing in the sea, it may or may not cause a tsunami. It would have no global effects.

IN DETAIL

No. It’s too small even to cause a tsunami, probably. If it hit the land, it would have major effects but only locally. Chances are it hits a desert or remote region that’s uninhabited or hardly inhabited - and you might get a few casualties, but probably not many. Chance of hitting a highly populated region is low. If it does, you’d get thousands, or even millions of deaths. But it is not big enough to have global effects.

With tsunami - then that’s not very well understood. But it’s different from a tsunami resulting from an earthquake. With an earthquake the entire floor of the ocean over a large area shifts up or down. But with a meteorite impact, the impact creates a temporary hole in the ocean which quickly fills up again. This means that you have a big wave goes outwards, but then it gets pulled back in again almost immediately. It’s hard to calculate the effects of this, but probably it has most effect if the asteroid hits in shallow seas close to the land. So the 800 meter asteroid - maybe it is just large enough for a tsunami if it is close to land and hits a shallow sea. The experts would probably argue back and forth on that.

You can use this calculator from Imperial College London to get a first idea of the effects of an asteroid impact. Putting in 800 meters, it would have major effects locally. At a distance of 100 km, wall bearing multistory buildings are blown down, most trees get blown down, windows shattered, and you will get a fine dusting of ejecta with occasional larger fragments, clothing, newspaper, trees etc all ignite. Calculated Results. It will make a crater over 17 km in diameter so you don’t have any chance of survival if you are within the region of that crater. Even out to 200 km clothing, newspaper etc ignites, but at 300 km you are safe from that. Glass windows would shatter. Calculated Results

That’s just one model of what happens, so to take it with a pinch of salt, but it gives a good first order idea of the results.

An asteroid 1 km or larger starts to have global effects, and from 10 km upwards, then it has major impacts on our climate for many years. But none of those would destroy all life on Earth. For that, you need an asteroid of several hundred kilometers in diameter. An asteroid as large as that would melt the crust globally and cause oceans to evaporate and the Earth would be sterile to some depth - but even then, you’d have some life still survive kilometers below the surface, probably.

However we haven’t had impacts large enough to do that since the early solar system. They stopped some time after the formation of the Moon. All the big craters and the lunar Mare on the Moon happened in a short time period of a few hundred million years - some think they may have happened over an even shorter timescale of just millions of years. The Apollo and other lunar missions in the 1960s through to the 1970s didn’t return enough by way of samples and data from the Moon to answer that question to that level of detail, because they only sampled a relatively small part of the Moon’s surface, so the question remains open.

However whether they ended 3.9 billion years ago, or just under 4.5 billion years ago, it hardly makes much difference. The main thing is we just don’t get impactors that big any more. This is clear from the cratering record of Mars, the Moon, Mercury and what we have of the geological histories of Venus and Earth. There are plenty of objects large enough to do that, but they are either in orbits that are stable at least for millions of years, in the asteroid belt, or they are beyond Jupiter. Jupiter protects us from the largest asteroids and comets by breaking them up, or they hit Jupiter or the Sun or are ejected from the solar system long before they can hit Earth. It doesn’t do such a good job of protecting us from asteroids up to a bit over 10 km in diameter.

Those can’t make all life extinct. At least a few percent of species will survive. And humans are great survivors. With just minimal technology, clothes, fire, boats, we can survive almost anywhere on Earth - many of us may have forgotten how to do so, but at the least, some of us would survive on shellfish, insects, fruit, seeds etc, and it just needs a few things like that to survive the impact, as they would ,and humans can cultivate them, travel to find them. We wouldn’t go extinct.

But we don’t need to worry about this happening at present anyway. The recent all sky surveys have been very successful in searches for the largest asteroids and we know the orbits of all the asteroids of 10 km or larger that could hit Earth. None are going to hit us in the next several centuries. We’ve found more than 90% of the 1 km ones and none of those will either. This is as expected because such impacts are very rare (not been any in all of human history) but we know for a certainty now about the 10 km ones and will find 99% of the 1 km ones by the late 2020s.

As for comets, at present only 1 in 147 is a comet, of the ones that pass Earth. That reduces the chance of a large comet 10 km in diameter or larger hitting us this century to a really tiny 1 in 100 million. We’d see a comet coming years in advance anyway, especially one that big, many years before. And Earth is such a tiny target, that it’s almost bound to miss us like the comet Siding Spring that had a tiny chance of hitting Mars but missed. But that 1 in 100 million is such a tiny figure we can ignore it. Smaller comets could hit us with a higher probability, but they are not the top priority of the searches at present because they also are very rare too compared with ordinary asteroids..

See also my Giant Asteroid Headed Your Way? - How We Can Detect And Deflect Them