Demonic Spiders: The Big Bull has a giant hammer that it likes to swing in a big circle to knock you down. It's hard enough on its own, but when you have two... Half Brutes are just as bad, since they're invincible until they discharge their electricity at you.
Ensemble Darkhorse: Most reviews of the game note that the Mummy is an infinitely more charming and likable character that Sphinx; his puzzles even seem to have much better designs than Sphinx's. At least one reviewer noted that they'd have prefered a game based on him. It makes a lot of sense from both a story and gameplay perspective. Story-wise, the main hero isn't given much characterization beyond being the standard fantasy "Chosen One". And whilst Sphinx's portions of the game are enjoyable, they're ultimately a Zelda clone with added jumping. However the mummy's tragic origin and the Big Bad's personal crimes against him allows players to invest more in his story. That's not even mentioning his fun gameplay sections are an entirely new concept dreamed up to take advantage of his new found undead state.
Goddamn Bats: The little tomato-looking Cyclops. Their modus operandi involves suddenly appearing, shooting you with a frickin' laser beam, back-flipping to avoid your revenge swing, and disappearing. When you do manage to hit the thing, it will split in two mini-tomatoes. Joy. Fortunately, striking it a second time will kill it.
Player Punch: When young Tutankahmen falls over and smashes the last vase. Such a stupidly written way to fail. After all that he still won't be able to get back whats left of his life.
That One Boss: The Geb Queen. Her attacks deal an obscene amount of damage and she is completely invulnerable unless bitten by (and here's the punchline) small spiders that Sphinx must release. Doesn't sound too bad, right? Well, that's before the Geb Queen decides to start summoning an endless stream of Skull Swordsmen. Not hard enough yet? The Skull Swordsmen will also actively target and kill the spiders to stop you from even getting a chance to hit the Geb Queen. So in other words, you have to get rid of her henchmen, release the spiders, make sure that the spiders survive long enough to give you a chance to hit the Geb Queen, and survive a barrage of enemy attacks that will drain your health faster than you can say "FFFFFFUUUUU--".
That One Sidequest: The "race along the beach" mini-game is rather difficult, not only because it requires avoid several monsters and not accidentally hitting the water, but because you must hit the lamp at the end in one shot. Miss it the first time, and no matter your speed, you fail.
The Woobie: Tutankhamen. Ends up killed by an evil bastard, posing as the brother he murdered, right in front of his betrothed no less. Then finds himself an undead Mummy who must inflict untold horrors on himself to escape his captor and attempt to get what's left of his life back. And ultimately fails to regain his mortal body after the Big Bad is defeated.