Boss Battles in video games tend towards two extremes. One type is the boss that take a very long time to beat, but poses little offensive threat; a boss that is a Stone Wall, in effect. This is the Marathon Boss. Then you have these — bosses that hit hard but die fast. However, these bosses are not necessarily easy, just as Marathon Bosses are not always difficult. These bosses can be Sequential Bosses, though this trait usually applies to individual forms in that case.
In game design, these models may be favoured for being more exciting than Marathon Boss-style wars of attrition, though if they die too quickly, players may be able to bypass whatever gimmick or strategy they were supposed to use simply by using an Attack! Attack! Attack! strategy. In addition, their attacks are usually difficult to dodge, since, obviously, dodging attacks would negate their offensive power.
Marathon Boss is this trope's inverse. See also Boss Vulnerability; these are usually type 1s.
Note that this is not merely a boss that goes down very quickly — that usually falls under Breather Boss or Anticlimax Boss. They must be able to take you down very quickly as well. Fragile Speedster-type bosses that frequently dodge attacks do not count either, since in that case it's as if they have high defense anyway. See Get Back Here Boss for that.
Subtrope of Rocket Tag Gameplay.
Not to be confused with Boss Rush, or a boss that rushes at you.
Whaler in particular; he turns into more and more of a Glass Cannon as the fight progresses, to the point where you can kill him in one hit if enough time has elapsed. In addition, his vulnerability wheels never fall off, making him the only boss that is actually capable of dying in a single hit.
The Bone Demon in MARDEK. It has the lowest HP of all the chapter 3 Bonus Bosses, but has very powerful attacks.
Jubei Yagyu in Onimusha Dawn of Dreams can unleash several quick and damaging swordslashes in a row, which is quite bad for your health. However, with a good defense timing you can pull an easy Issen counterattack and finish her off in two or three attacks.
Both final bosses of Alpha Protocol. One uses a series of deadly miniguns but has horrible damage resistance, while the other uses a rocket launcher but can be defeated in a single punch (although getting close enough to do so can be a problem).
Ridley in the 2D Metroid games, due to being one of the few (if not the only) boss who is always vulnerable to attack. However, you usually fight him in a cramped space, and his attacks are both hard to dodge and powerful.
For Alundra, the US localization team specifically noted that they tweaked a few bosses to have more attack power and less HP than in the original Japanese version, because they felt some of the Boss Battles were more tedious than challenging.
In the flash gameLARRY and the GNOMES, the Purple Monster boss has the least health of all the bosses; however, its attacks reduce a lot of health with a single hit, it attacks very rapidly, and its charge can kill you quickly if you don't dodge it.
In contrast to the series's love of the inverse, most boss fights in Final Fantasy V are of this trope. The first legal and decent release of the game outside of Japan was on a portable system, which was suited well to this trope, luckily.
The duel with Luca Blight in Suikoden II. Thanks to the prior Sequential Boss fight, he only has a sliver of health left, but he's still strong enough to kill you in two attacks.
Many of the DPS Race raid bosses in World of Warcraft have enrage timers that are notably shorter than bosses who are more of a battle of survival (typically 5 or 6 minutes, compared to standard 9-10 minute enrage timers), and the greatest danger is most often killing them before the timer expires and they start one-shotting the raiders.
Odin is a common Rush Boss in the Final Fantasy series as a whole, since he will generally give you a short amount of time to kill him before he uses Zantetsuken (which is either an attack that is almost impossible to survive or a Non-Standard Game Over). At the same time, he tends to have less HP than bosses of equivalent difficulty.
Most of the key bosses in Diablo II are marathon bosses (including all the Act Bosses except possibly Andarial, who's a bit of a half-way house), but the mid-act boss in Act 2, The Summoner, is a classic Rush Boss. He's extremely fragile, going down in two or three hits, but depending on your build he can easily One-Hit Killyou, at least on Normal difficulty. He also has fantastic range (well over your character's sight range), meaning new players often die to him before they even see him.
In Dissidia: Final Fantasy, many of the Golden Manikins are set up like this: They have so little HP (sometimes only one) that even a level 1 character can kill them in a single blow. However, their bravery/attack is often high enough that they can kill a level 99 character in a single blow, and are usually programmed to be aggressive, evasive, and use their best attacks.
Professor Hangar, the boss of Titania in the original Star Fox, has very light armor but his attacks are tricky to dodge. Typically, one of you will be dead within 30 seconds.
Bosses in the Izuna games tend to hit very hard, especially with their special attacks. But you're just as dangerous to them as long as you use items and talismans well instead of just hacking away.
The Bonus Boss of The World Ends with You, Panthera Cantus, can be defeated in as quickly as 35 seconds. However, he is also the single most damaging enemy in the entire game; even at level 100 and with severely-boosted HP he can still wipe the floor with both of your characters.
Raivolt in Grid Warrior. It doesn't have that much health, but it's fast, can stun you then charge at you, and its attacks deals armor-piercing damage. Its Desperation Attack can be a One-Hit Kill if you don't avoid the laser which stuns you, then it lands on you to finish you off.
In Hellsinker, the boss of Segment 2 Lead, the Scarlet Queen, has a hidden form if you defeat her with high enough Stella. The good news: it's only 15 seconds long. The bad news: It's particularly brutal.
The Four Kings in Dark Souls are best fought by doing as much damage as quickly as possible because you start fighting one but a new one enters the arena every minute until you've done enough damage to them together, making it harder to fight the ones that are already there without dying. In practice, they're either a Rush Boss or very difficulty Wolfpack Boss. They're often consider the hardest boss in the game simply because this is so different from the rest of the game, which encourages you to fight slowly and methodically.