What is the hardest cockroach to kill?

German cockroach !

The German cockroach, Croton bug or Steam fly (Blattella germanica) is a small species of cockroach, measuring about 1.3 cm (0.51 in) to 1.6 cm (0.63 in) long; however, they are known to get bigger. It can be tan through brown to almost black, and has two dark parallel streaks running from the head to the base of the wings. Although it has wings, it is unable to sustain flight. The German cockroach is one of the most common and prominent household cockroaches in the world, and can be found throughout many human settlements. These insects are particularly fond of inhabiting restaurants, food processing facilities, hotels, and nursing homes. In colder climates, they are found only near human habitats, since they are not very tolerant to cold. The German cockroach is originally from Asia, it is very closely related to the Asian cockroach, and to the casual observer they appear nearly identical and may be mistaken for the other. This cockroach can be seen in the day occasionally, especially if there is a large population or if they have been disturbed. However, sightings are most commonly reported in the evening hours as they are most active at night. This type of cockroach can emit an unpleasant odor when excited or frightened.

The Flying African Spike-Headed Fart Cockroach

Japanese female cockroaches. about the size of a golf ball, when you try to spray em they come flying right at you. its terrifying

The intelligent one.

The one that hides and/or moves very fast