Sarasaland Adventure v4.0 (SMBX) - Sky Castle (6-8)
Info: https://rpgmaker.net/games/4216/
The sixth castle is definetly on the difficult side as there's not only moving blocks (some with spikes on them) to deal with, but there is also a rather treacherous lava section to traverse, as well. The spiked pillars from 4-8 are back, too. Extra caution is needed in this level for sure.
One tip is that if you're quick enough when the level starts, you can enter the first room and get onto that moving stone block before it rises too high. If it does rise too high, you'll have to wait until it descends, then ascends again, and this can take over a minute because that block moves very slowly. Another tip is that if you have Raccoon Mario, you can fly up to the green pipe in the first outside area and skip the rooms to the east.
Wendy is a difficult fight because she is quick, her fireballs are quick, and it's hard to avoid them (and Wendy herself when she's in her shell). There's also podoboos and lil sparkies in the room, as well, which need to be avoided. Best thing you can do is to shoot her when you can. There is a little quirk here where Wendy can get herself stuck on one of the small cloud inclines; if this happens (which it did here), that gives you a bit of breathing room to either try to go for a power-up or to get some damage in on her.
Next is World 7.