How much of a fleet will it take to kill a OPS Pirate_Station of a 100000 ???

First, it would be advisable to destroy the planetary protection with gravity cannons - then you need a lot less fleet to rob the 100-K-OPS .....

second.... if it is still possible to destroy the grenadizer with interplanetary missiles, then this is also advisable .. Firing 35-45 at the same time should be enough .... if the OPS has 10,000 missile interceptors - then there is no point in trying to destroy the grenadizer with interplanetary missiles ...

after that it's easy - exact fleet size depends on the technology you have ... this can be enough without a grenadizer with a fleet of around 110-K to 150 K .... I personally used a little more in this case, as I happened to rob players with this fleet in the vicinity and only used the 100,000-point OPS as a gas station had (there were 4.7 million gas) .... https://xcraft.net/battle/index.php?battle_id=8f2cd81c06a3f439e36cc639185d7743
If the grenadier should still be present, it is advisable to shoot the grenadizer first in combat ... it is not that strong either - that should be completely sufficient with a 130-200 K fleet (depending on the technology) - according to my personal Assessment......

It is not advisable to use flagships while the grenadizer is there ..... a well-structured war fleet also works ... in an emergency, if there are problems with fuel, you can fly the war fleet to the OPS at a lower speed .. ... The type of attack is occupation and from the occupation then immediately further with transporters under attack or in occupation .... It is ideal if you have already cleared the OPS after 5 minutes and leave it - a longer occupation of an OPS is risky ..... I've already killed players who had slept while occupied on an OPS ..... https://xcraft.net/battle/index.php?battle_id=cab9971f0d0158387f6c24baf33be1bd (is an older combat example of a player who was too long in the occupation on an OPS - and was not the last one I killed like that)
once the OPS has been cracked, you can attack it again the next day with a significantly smaller fleet and actually every day ... the OPS produces new resources and slowly builds up the defense - it is easy to rob an ailing OPS. ... you can also look around in your area, where there are already cracked OPS stations whose defense is lower ...