One of the most classic and old examples of dirty marketing was John D. Rockefeller’s way of gaining a monopoly on gasoline sales for his company Standard Oil in the pre-WW1 era.
I am oversimplifying, but this was the general idea of Standard Oil’s dirty marketing strategy:
The prices were different, but for illustration purposes, let’s assume that it cost 20c a liter to produce gasoline and have it available at a gas station.
Let’s assume that Standard sold gasoline for 50c a liter in all its stations. Once in a while, a competitor would open an independent station and sell gas for less — say 35c.
Standard would then open a station next door and price its gas at 10c per liter. This means below cost for the sole purpose of driving the competitor out of business.
Of course, before it became illegal and was correctly classified as “unfair competition”, this cutthroat tactic was what made Standard Oil the most profitable company in the world (at the time).
Microsoft did something similar by packaging so much free software with Windows that other operating systems could not compete. Unless like Linux they gave their systems away.
Ultimately, USA and EU regulators have fined Microsoft for this kind of bundling and many other marketing tactics which regulators considered unfair competition or dirty marketing