Spiked walls that can be sneaken into enemy grounds... Did I say that they can't be destroyed with one charge of explosive as well? Oh, what about 42 base damage with secondary attack? Pack bonus defense anyone?
You know a creature is strong when just 8 of them can handle a wild giga even without being riden, having a saddle or even needing a Yuty buff. Useful even on PvE.
Let's get straight to the point. Kentrosaurus is going to be a cut above. It's piercing gaze alone will be enough to send even the largest carnivores running. It will slash the competition. Tribes would be foolish not to stick this in their arsenal. It may be a hard tame, but I'll take a stab at it. Did I mention that it's pointy?
Where would you even put the saddle? The only “clear” spot I see is the neck or head, and the poor guy could not even hold your weight on its neck or head. Then again, you could have an elevated saddle over the spikes.. that would be impractical. Too small to carry you, but great for tribe-angering.