Complex sentence: Some people consider "The Reaper" the first antivirus software ever written-it may be the case, but it is important to note that the Reaper was actually a virus itself specifically designed to remove the Creeper virus.
Split into simpler sentences: Some people consider "The Reaper" the first antivirus software ever written. This may be the case, but it is important to note that the Reaper was actually a virus itself specifically designed to remove the Creeper virus.