[quote=@NacNak]
[quote=@ASTA]
How are you going to navigate through buildings built by normal-sized aliens? They aren't going to engineer or erect doorways that cater to the morphology of mega-scale reptiles that are fifteen feet tall.

Even the ten feet tall creatures are boldly pushing it. Seriously, that's roughly two feet taller than an M1 Abrams MBT, which by no means is a small vehicle.

The way you've designed them, these guys are going to get ganked by smaller aliens with horrifying ease. Sheer physical strength might be ideal for sword-and-shield combat, but that's not going to cut it with smaller soldiers that are wearing powered exoskeletons and wielding hand-held infantry weapons that make modern anti-material rifles look like low-powered matchlock firearms.
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... you have an exhalent point, but then again, the Zargan's wouldn't be the ones navigating through buildings, that'd be the Sas-Zak since they're roughly over 6ft tall =3

And the way I see it, if one Zargan was to come across a group on alien soldiers all around roughly 6ft, it be like Titanfall, where a team of pilots are going up against a single Titan Mech, except the pilots are harder to kill and more tedious to deal with, but that doesn't make it any easier to take the Titan down, and if you have a group of alien soldiers and a group of Zargan soldiers, it's be like a team of harder to kill pilots vs a team of Titans, if that makes any sense =3
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And then one soldier comes forth with a light anti-tank missile launcher and settles the fight then and there. 

It's worse if these giant reptiles unfortunately find themselves trekking through urban environments, which is where most armored vehicles are at their weakest on account of the prominent number of areas from which ambushes can be launched from, the ever-present threat of concealed mines and IEDs, and the blind spots a bulky tracked vehicles is naturally afflicted with.

The giant reptile isn't a tank, but it's still ungodly huge and therefore is bait for every bog standard trooper with something heavier than a battle rifle. It's not going to have the same amount of armor a tank has either because of the shape of its wearer and the mechanical problems that come along with elevated degrees of weight.

I'm not trying to slam your idea, but massive aliens like that being conquerers doesn't make much sense. Their size is a horrible (and easily exploitable) disadvantage and the ten-footers aren't going to fair much better either.