I would just like to point out - after a good half-hour of switching back and forth from PP's table - many of the dots on the chart represent exiles as well mortalities. For instance, out the eight dots for the year 52 BCE, only one represents an actual death - the rest were, for multiple reasons, exiled.
Further, although it has been suggested that the late/mid first century BCE sample bias has been offset by the absence of Cicero's letters, a sample bias is still apparent. Take, for example our sources for the early period of the civil war (Gracchus to c.Sulla's death). These are mostly synoptic histories (Appian, Dio, Livy etc.), and only really documented the lives and deaths of the most notable individuals: the men whose actions could make or break history. Less notable people are only mentioned when could be use to prove a wider philosophical argument.
The sources for the mid century conflict (Catiline to Caesar) are also aided by these synoptic histories. These, however, only play an auxiliary role in the reconstruction of this period as they give way to other, more comprehensive and near-primary sources: Sallust, Caesar and Hirtius. Both the comprehensive and primary(ish) nature of these sources mean that the deaths of historical footnotes were recorded alongside those of the famous republicans: Hirtius and Caesar mention the deaths centurions and primi pili; Sallust mentions the deaths of Catiline's legates.
So for a greater insight into who killed the most, one is better off looking at figures from synoptic histories.