The problem here is one that I'm working out for my own game. The problem really is that modern equipment REALLY breaks the D&D world. My fighter dressed Second Chance Hard Core body armor could very calmly walk through an arbitrarily large number of orcs because the orcs essentially have zero chance of actually hitting him. He's going to run out of ammunition quickly at which point it becomes a stalemate. The orcs can't hit him, he can't hit the orcs.
A hamatula would likely have some trouble with a single tank. He can only teleport so far and his visual acuity is likely good to a range somewhat shorter than the range of his teleport. Thus, if the tank knows that the hamatula is coming, it can likely maneuver to a good position from which to attack the hamatula. If the hamatula were to suddenly stumble onto the tank, then the tank is well and truly fucked because it has no close-in weapons systems other than the coaxial machine gun.
Orc horde vs a special forces unit? My money is on the orcs. The reason for that comes from historical evidence. The orc horde's only chance of success is to roll right over the special forces unit by weight of numbers. The answer to large numbers is, and always will be, firepower. The Chinese used this tactic in Korea and it worked VERY well at first. A special forces unit lacks the firepower to repel a massed attack like an orc horde. Their weapons aren't that heavy and they can't carry enough ammunition for the weapons they DO have. Now, at some point they'd likely mow down enough orcs to trigger some kind of morale check among the remaining orcs. If they fail that check, then the attack breaks and the orcs retreat. That works, but if the orcs succeed on that will check, then the SFU guys are fragged.
Kraken vs Submarine: Submarine all day every day. Modern attack submarines can, quite literally, hear whales humping. A creature the size of a kraken cannot POSSIBLY be silent under water, ESPECIALLY when swimming fast enough to effect an attack on another submerged target. The kraken closes to within a few miles and is promptly greeted with a pair of Mark 48 torpedoes and 500 or so pounds of torpex. Instant calamari.
Enterprise vs. Cthulu: Well...I think Cthulu's power of causing insanity is based on line of sight, rather than range. Since MOST of the enterprise's crew would never see Cthulu, no problem there. Now, it does occur that, given the large number of computers and data systems aboard the enterprise, there must be a fairly large IT staff aboard. That being the case, they should already know how to deal with the likes of the Great Old Ones. See
www.userfriendly.org.