Any guides on challenge mode?

[Lockdown]

Having a tough time with combat challenges... I played through the entire game without using much 'variety' or knowing how to really be flashy and score points

I haven't really found a good guide

[BloodyMares]

Variation Bonus consists of: Strike (10). Counter (10), Evade (Redirect), Stun, Special Combo Throw (50), Special Combo Takedown (50), Ground Pound (100) and Gadget usage (Batarang or Batclaw - 10), Titan Strike (25), Titan Takedown (100).

Dark Knight Bonus (500 each round): Don't get hit
Perfect Knight Bonus (5000 in the end of a fight): if completed a fight without being hit.
Flawless Freeflow Bonus (1000 each round) : Don't lose your combo.

Also, during a fight there can be environmental takedowns (100) if there are electric fields. Ring Out (if a thug falls from arena) gives 25 points.

Tips:
To make a fight easier, jump over thugs. That way you won't get hit and won't lose your combo.
if there are more than one knife wielders, perfrom combo takedown on one of them to make a fight easier.
If you want to finish a fight with Ground Pound but there's only one guy left, use Batclaw on him and Redirect. This way he quickly falls to the ground and you can finish him.
If there are titans in a fight, always try to jump on one and then hit another until you can jump on another one. That way you probably won't get hit and deal with guys and titans at the same time.

[MaximJay]

Nice guide!

Added: Try to knockout enemies with a Ground Pound if possible (it multiplies your combo by 100 each time). Also make sure to vary your attacks as much as you can to stack your Variation Bonus (up to 3500)