If you're talking about WMDs, I'd imagine the WMDs in Disco verse would no longer be simply "blow everything up and killing everything" like the current H Bombs.
In my opinion, a weapon capable of system wide total devestation would be the least powerful thing we'd have.
All WMDs must be strategic, there won't be a point of doing massive collateral damage to an area as well as killing the enemy would there? If that was done, when you occupy the area you'd have to invest in building the infrastructure and defences again.
Therefore, strategic WMDs should concentrate on wiping out the enemy living force - people. Something similar to radiogenic weapons and biochemicals would be used.