How can i destroy these ship class?

[Fyron]

Overcoming a large racial combat bonus disadvantage is often very, very difficult... Use smaller ships (such as Battleships), so that they move a lot faster in combat. The loss of damage when comparing the Massive Mounts of baseships with the Heavy Mounts of battleships and dreadnoughts is not that large. Your ships will also get a nice 40% defense advantage from not being baseships (as baseships get a 40% defense penalty), as well as being able to move faster than dreadnoughts and a lot faster than baseships. Set them to Point Blank range. This will allow them to get close and stay close to the enemy ships, to maximize your chances to hit. Before they are sent sprawling backwards of course...

Perhaps employ Wormhole Beams. They will fling the target ship to a random square on the combat map. Break up his fleets to make them easier to deal with.

Another option is to use high damage per shot but slow reload rate weapons. Since your ships are being flung away and unable to return to the fray, make them do as much damage as possible in that one round that they can... Perhaps Null Space Projectors would help. Do damage to the internals of his ships, bypassing shields and armor. Tachyon Projection Cannons (weapon damaging weapons) might also be an option, to try to disable his weaponry. They aren't too effective in the long run though...