I just finished Batman, Robin, and Nightwing in one day using this strategy after struggling for a long time starting with Catwoman. Ironically, it was a great start as I stumbled across the easiest, foolproof way to do it. Thought I'd share after all the strategies I've read don't really seem to help.
For anyone who needs help getting this result, read on.
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Terms
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Get Flawless Freeflow as Batman, Nightwing, Robin, and Catwoman in the Monarch Theater.
Note that this basically means you need a full combo from start to finish. No damage is required, so you can take damage before you start your combo, but basically to keep the combo you can't take damage anyway.
At the end of each spin, check the Perfect Freeflow bonus in your score breakdown to confirm it has registered.
Note that PERFECT KNIGHT at the end of Round 4 just means No damage for 4 rounds. That's not what you want. It doesn't mean 4 rounds of Perfect Freeflow.
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i-frames
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So first off, here are the invincibility frames you need to know about:
Y+B Combo Takedown.Re-direct Air Attack on Shielded Enemy (B,A,A)The third is the key here. Armored enemies are easy to spot and you can reliably target them most of the time. As long as you smash the B's, A's, A's quickly, the i-frame will reliably activate .It gives +2 to meter too. Note that only air attacks on shields are i-frames, air attacks on other enemies are not.
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The strategy
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Because you can't afford to drop the combo, you basically want to grab that i frame as much as possible to build a counter and stay safe. Start looking at Shields as your friend, not a combo threat. see one, go for the Aerial Attack i-frame. Just be sure to nail them with it.
When you have enough counter, run the combo takedown on NON-SHIELDED. That's the key. Shield i-frames are your friends. You don't remove them. You leave them available as a safe way to create a combo. Reduce the unshielded rapid instead. Also, the Combo Takedown itself is i-frame, which means you stay safe by switching between these two i-frames.
In between, you need to Re-Direct relentlessly, and for the safest result, it's best to buffer the input before your current punch or i-frame ends. This saves you from being late with your input if an animation ends a bit earlier than expected. I tap at least three times, by the third they usually skip.
Also prioritize safety. Stay away from crowds and have some distance from everyone. When in doubt, redirect. You can redirect infinitely without dropping the combo and dodging (without flipping an enemy) Once.
To summarize,
redirect continuously until you find an enemy safe to hit, after which you hit them once and redirect immediately. If you find a shield, enter the air attack i-frame, but for shields, make sure you are going to nail them 100%. Dial the combo to 5, then Combo Takedown all unshielded. Don't try to be fancy. Whether you do a Combo Takedown, Air Attack, Just Hit, or even manage to Counter, make sure to buffer the redirect before the current animation ends. Keep redirecting until you are 100% sure of what you are about to do. Clearly see the targets first, whether they are protected or unarmed, or more importantly - if they are on the point of picking up a shield. Don't be in a rush. The shadows in the Monarch Theater can sometimes confuse you and interfere with visibility. Be absolutely certain. There is no rush.For the guys you have to use your first combo counter first to eliminate the Brutes. Stay far, far away from them until you are ready to eliminate. Then all 4 characters play the same because this strategy negates all inherent differences in move sets and attack speed.
Literally, once you get it, you can beat it with all 4 of the same.
GOOD LUCK!
