A weapon that could create antimatter at a remote location would be a particle accelerator. One that could create non-trivial amounts of antimatter would cause far more damage from its direct consequences than from antimatter. By factors of millions or billions.
It would be heinously expensive and would require the kind of energy input that only gigawatt-grade nuclear power plants could provide. Rather than using a complicated, failure prone and inefficient way to transform nuclear fission into destruction, it would be simpler and more effective to lob a nuke with the same amount of uranium or plutonium.
Hence, for your day-to-day megadeath needs, thermonuclear weapons will remain the tool of choice for the foreseeable future.
To build either nukes or particle accelerators you need physicists, who are the kind of non-team-players likely to point out that nukes would work better.
It would be heinously expensive and would require the kind of energy input that only gigawatt-grade nuclear power plants could provide. Rather than using a complicated, failure prone and inefficient way to transform nuclear fission into destruction, it would be simpler and more effective to lob a nuke with the same amount of uranium or plutonium.
Hence, for your day-to-day megadeath needs, thermonuclear weapons will remain the tool of choice for the foreseeable future.