What happens if a freaking big meteor hits us

In brief, nothing good. From the explanation (slightly edited to fix translation glitches, a few left in like "Star of the Death" :-))

The diameter of the meteorite is slightly larger than the breadth of Honshu Japan. The collision point is located 3,000km south from Japan, in the ocean. The velocity of the meteorite is 70,000km/h, although it appears to approach slowly because of its size.

The Earth's crust to a depth of 10Km is fully peeled away at impact, debris reaching heights exceeding 1000Km, much of it leaving the atmosphere altogether and reaching space. The impact crater's outer edge is 7000Km in height, resembling a mountain range. The crater's diameter is 4000Km, roughly large enough to swallow an area from Guam to the Chinese continent.

The impact shock wave reaches the Japanese Islands, which are crushed (Goodbye Tokyo). But, it was only an introductory chapter of the tragedy that would start in the future... (sic)

The following blast wave, made up of vaporized rock, with temperatures exceeding 4000C, reaches the Himalayas within three hours after impact, melting snow instantaneously. Within 24 hours, the blast wave will reach the Amazon Basin, igniting all it touches. Eventually, a blanket of fire will enshroud the Earth for more than a year, boiling away the world's oceans at the speed of 5cm per minute. The naked sea bed is exposed to the intense heat and melts down like lava. At this point, the earth becomes a star where the living thing cannot live. Thus, the earth turned into the star of the death...