Final answer:
Hydrogen peroxide is the high-level disinfectant that does not require activation or mixing and has little odor.
Step-by-step explanation:
The high-level disinfectant that does not require activation or mixing and has little odor is Hydrogen peroxide. Hydrogen peroxide is widely used as a household disinfectant due to its effectiveness and safety. It breaks down into water and oxygen gas, making it environmentally friendly. Additionally, it is inexpensive and readily available.