As for Lucas, our down throw to up air confirm is true starting from around 0% (regardless of DI) but it will not start taking stocks until we meet the right conditions as far as Lucas rage and the opponent's percents goes. If an opponent is likely to airdodge not knowing that our confirm is true we can extend the percent it will work at by waiting for the airdodge to end and punish it.
The reason some of us do not use up air at early percents is because it can stale our up air if we decide to use it later in the match when it is time to take stocks and dair is our aerial that deals the most damage so some of us would use that instead.
As for up air outside of the kill confirm, I have heard in the server thar our up air is safe on shield as far as landing go and it can be used when falling or for hitting through platforms if lucas is below them.
But since our up air hitbox is really small and is a fixed hitbox that will not move with Lucas's head it is reallly frowned upon in the server since it is too hard to hit or too much work so the thought of landing with it is written off and discouraged.
Going back to the down throw up air confirm, once it stops working our up throw is guaranteed to kill since the percent gap between our up air confirm and up throw are literally next to each other.
As for greninja being our worst matchup, that is the answer the server usually replies with due to what PK Bash said earlier, along with the fact that Greninja along with Palutena and Fox are written off for our footstool combos since it is difficult to land footstool combos on them starting from 0 to low to mid percents (30% to 70% for me as an example). So that is discouraged too.
Another thing is that some of our western Lucas mains in the server tend to get knocked out in pools of tournies that they attend further popularizing that greninja is our worst matchup. Then there is the vod of Mekos vs Greninja in a wifi tourney where he lost which can make the feeling sink in that we lose the matchup.
Video:
https://youtu.be/-aqbbqOclbY
I made a long post about the greninja matchup for Lucas that talks about options both have in the matchup in the 4br V2 thread.
Either I plan to edit this post with it, or after someone comments, I'll make a new post that will just a copy and paste of my old Greninja post.
If you guys want the charts for our up throw and up air kill percents. I can share them or you can snag them from the lucas discord server.
EDIT: Besides the Lucas mains in Europe, Luco also thinks differently about the greninja matchup and does not think the matchup is as horrible as our server makes it out to be since he has Waveguider, a wii fit and greninja main in his area.
EDIT 2 (Found it):
"From the discussions held in the Lucas Discord, I think this opinion is based on multiple Lucas mains losing to Greninja players in offline tournaments. Some of us say that it's due to Lucas have trouble hitting Greninja on the ground with his idle pose (slightly lowers his hitbox) and having a hard time landing footstool to jablocks on him. Uncharged water shurikens are hard for some Lucas players to punish or get around due to the lack of hit-stun applied when we reflect it with our f-smash. The uncharged water shurikens can be shielded by Greninja (if I'm right) if he spaces them well; they also can cut off some of Lucas's aerial approaches from afar since they are fast which can frustrate Lucas players if they get hit by them.
Even if they decide to take a grounded approach they will still have to deal with the shurikens which seems to be a hassle for the Discord Lucas players right now. Furthermore, a fully charged shuriken can be shielded by Greninja unless thrown near or at point blank range.
Next there's Greninja's Hydro pump which can disrupt Lucas's PK Thunder recovery. I do not have much to say on that besides adapting, mixing up pkt angles, mixing up recovery, and getting to know PKT 1 (the orb) better so if a Lucas does get blasted away by Hydro Pump during their PKT 1 they may have a better chance at surviving and making it back to the stage.
Greninja's air to air combat is fine, his bair comes out at frame 5 which beats all of our aerials, while his up air comes out at frame 7 which is the same for Lucas's up air. Greninja's fair comes out on frame 16 and lasts until frame 17 so the whole hitbox is only 2 frames while have a lot of endlag (first active frame is 55) compared to Lucas's frame 9 fair (first active frame is 42). I think Lucas players should space their disjoints of fair while avoiding Greninja's fair air dodge read attempts.
Greninja's up-tilt is great for catching Lucas if he jumps right above Greninja or decides to land on top of Greninja with a nair. I'm not sure if Greninja's f-tilt is longer than Lucas's but I do know that ours has a disjoint so we can win a trade if they are both spaced, plus Lucas's f-tilt comes out quicker than Greninja's (frame 7 vs frame 10). The same can be said frame data wise for Jab 1 (frame 2 vs frame 3) and down tilt (frame 3 vs frame 9) plus ours has a disjoint at the very tip that is not a hurtbox.
Greninja's n-air comes out on frame 12 while also having a larger hitbox and base damage of 11 which makes for great shield stun vs Lucas's frame 7 n-air with a base damage of 2 with the final hit dealing 4 which can make for some very small shield stun.
Oh, I almost forgot greninja's footstool setups which can inflict a good amount of damage or take a stock at the right percents.
Conclusion: I think some players of Lucas Discord may get easily frustrated not having their way with Greninja, with their main concerns being gaining little to advantage in attempting to "counter" water shuriken, to greninja's size, and players going on tilt when hydro pumped offstage."