Deltarune: Chapter 3 - Susiezilla (T-Rank)
The floaty controls took a bit of getting used to but I found this pretty fun after awhile. The movement is very physics-based so you can get a better handle on the controls if you can account for things like momentum and inertia.
T-Rank requires the max of 800 points, so getting the 99 Popularity Bonus on all 3 phases is basically mandatory. The tennis balls deal the least amount of damage, and Tenna can take 1 hit from them at maximum. Any more than that, or getting hit by anything else to begin with will disqualify you from the bonuses.
Memorise when the big tennis ball shooter waves form (at 28 points and 214 points) so you can get into position to eliminate a lot of them quickly. If you get overwhelmed, go back to the centre and focus on deflecting the tennis balls instead.
When Spamton appears, don't kill him too quickly because you can farm a lot of points from the enemies that continually appear. Notably the bulldozers give a whopping 10 points each.
The final Shadowguy wave gets smaller based on how many points you have (800 minus your current score) so it's entirely beatable if you have enough points by then.
Be especially careful about recoil from hitting the front of a bulldozer or from hitting Spamton, those can send you flying if you approach at a bad angle and you'll rapidly lose control. I find it best to hit Spamton as horizontally as possible so you just get bumped back instead of pinballing off the top and bottom.