If I remember correctly, Haber freed up a great deal of labor to be put into the Germany's military complex which empowered the country for WWI which embittered the country leading to WWII.
I think nitrogen run off from soil has had quite an impact on changing water habitats as well, eutrophication and fish getting beat out by algae for limited oxygen resources.
On a (slightly) smaller scale he also figured out how to weaponize chlorine gas and heavily evangelized its use (to the extent of bringing a tank to the front against orders and releasing it at Ypres).
As father of chemical weapons he oversaw their use on the battlefield and gave the world Haber's rule for more effective mass gassing. Mustard gas too, and I think he even had some part in development of Zyklon B.
He was completely unapologetic about it - he thought gas a better form of killing.
Both his wife and daughter seem to borne some guilt from his poison gas work. His wife committed suicide a week after Ypres - though some have disputed if it was connected. His daughter's suicide was on learning her research into poison gas cures couldn't be continued.
I think nitrogen run off from soil has had quite an impact on changing water habitats as well, eutrophication and fish getting beat out by algae for limited oxygen resources.