Kengar, could you demonstrate some other rules systems in which a normal -- no class levels, nothing special about him at all, and in this rules system he's considered an acceptible monster to send against just-starting-out heroes -- goblin can kill the most powerful player character possible with a single lucky strike?
Now, if you gave the goblin a morningstar, the weapon it is using in the monster manual, and if it rolled a critical hit, and if you were using the d20 Modern damage threshold instead of the D&D damage threshold, you could conceivably do 14 points of damage (2d8-2 for strength), which would force a massive damage save on anyone with a Con of 14 or lower. But you've specified a dagger, so that's out.
I'm not using traps, either, since what you seem to have in mind is a "no environment, no special circumstances, just one guy and a goblin in an arena, with the goblin having nothing but a dagger and the hero having all his equipment" fight.
It is statistically unlikely, but not impossible, for a goblin to kill a high-level character in D&D. I mean, thousands to one odds, yes. The easiest way would be for the goblin to disarm the hero with an incredibly lucky roll and then use the hero's weapon, and then roll a critical hit incredibly luckily, and so forth. Not completely impossible. Unlikely, yes, but not impossible.
So, if that's the test, please show me a system where a completely equipped character at the highest level (point value, whatever) achievable in the game, and who is combat-maximized (ie, not a GURPS guy with no points in combat), has a significantly better chance than the D&D guy of dying at the hands of something he was expected to beat when his character was first starting out as a brand-new recruit.