Red Rain of Pain

Weapon

"a katana hilt" which can project a force field that can cut through anything. The force fields under attack routinely glow red and orange and then all the way up through the spectrum until they reach violet and black and break down. The efficacy of the field is directly proportional to the cube of the velocity or to the momentum of the object it resists. It can recharge its energies by soaking up the kinetic energy of the projectiles it stops. A traditional force field that converts the energy of an attacking force and repels it back on itself.

He channels his forcefield into a deadly blade that can take any shape he needs to effectively slice and dice his enemies. The blade itself is invisible unless someone's a seriously good fighter and can see ki. It could be explained that his killing intent was so strong even without a sword, so his ki made him one.

Techs

Bakudan: Creating a small force-field inside someone’s head and expanding rapidly. Applied this to pretty much anything; even heavily-armoured robots. In more powerful circumstances, he can also use this to ensure an escape via removing obstacles; making them explode from within.

Kamaitachi: Telekinesis. Creating a solid field of force and moving it, and when he gets it to work really precisely, he ends up with TK.

Kamikaze: Variety. Once he enters Kamaitachi, the next step is precision application. He can do anything as long as it involves the term ‘movement’. Like hyper-accelerating the vibration of something’s molecules via the creation of super-tiny forcefields, and heating it up significantly. Use tiny super-precise force fields to nudge the electrical synapses in the brain for Mind control. Create a tiny forcefields shaped in just the right way and accelerate it really fast into someone? Metal Storm.

Sub Techs

Thermal insulation: A double wall with trapped air can be used like thermal insulation, like a coffee thermos. If he removes the air, he removes any chance of conductive heat transfer.

Sound insulation: A double wall with no air between them will effectively cut off all sound – no medium for the sound waves. Then again, when his force field is already perfectly rigid, then it won’t transmit any vibrations, but it will reflect them perfectly.

Secret communication: A force field in the shape of a parabola can focus incoming sound to a single point (like a telescope for noise), effectively providing super hearing. Do this with two force field parabolic “cups” so he and his allies across the room can whisper to each other without people in between hearing much of anything.

Eerie Noises: While he could try to make a vibrating force field to generate sound waves, a simpler method would be to simply shape his force field into a flute, empty jug, or a hollow reed. The natural air flow blowing across such a thing would make noise that could be used as a signal in a covert op, to distract a guard, or to play a soothing melody.

Anti-Bloodhound: As an addendum to making a bubble of air, one could encase themselves in an air tight bubble to foil scent tracking dogs. To further trick them, he could trap some air around him with his scent and send it off in a leaky bubble leaving a false trail for super noses.

Textures: when he has fine control over force fields, he is be able to alter the surface texture. If his allies can read brail, he an imprint invisible and silent messages for them. This could also add to a visual illusion. A holographic brick wall backed up by a force field can be pretty convincing; if it actually feels like brick, who would know the difference. Also, a rough surface can slow a run-away object down to bring it safely to a stop – not all movement needs to be arrested by a sudden and violent smashing into an instant wall. Alternatively, a suddenly glass-smooth surface could be inconvenient for a pursuer. As a nod to power limitations, stopping a speeding car takes a lot of resisting force, while slowing it down with rough force fields requires much less resisting force.