Some of the sprites are marked with small letters/numbers. I should explain.
Unmarked - These are the three primary members of the family. Their names are written in corresponding order to the side.
SP - EXE3 added this fourth and strongest virus level, which stayed for the rest of the series. Its name is simply the first family member's name with "SP" attached to the end, unless otherwise noted. In EXE4 and EXE5, the pallettes used for the SP viruses in EXE were used for the third EX virus (see below), but as EX viruses were done away with in EXE6, the SP naming system returned. In the english versions of BN3-5, "SP" is replaced with the Greek letter Omega, and in BN6 it is a "SP" like in the japanese version. Example: Fishy family from left to right is Kiorushin, Birdraft, HellCondor, and KiorushinSP. In english, Fishy, Fishy2, Fishy3, and FishyOmega.
1EX/2EX - EXE4 and EXE5 used an additional two levels to place in between the three main members of the family. For the naming scheme, they use the name of their immediate predecessor with "EX" attached to the end. The third main family member gets a corresponding "EX" version as well, but since for the most part the "3EX" colours correspond directly to the SP versions of EXE3, I use the "SP" marker in place of a "3EX" marker. Example: Gear family from left to right is VorterGear, VorkerGear, VorkerGearEX, VorzarGear, VorzarGearEX, VordrolGear, and VordrolGearEX.
R1/R2 - In EXE6, the "EX" viruses were replaced by "Rare" viruses, which served a special purpose and as the name suggests, were extremely rare, only appearing in one battle-group in one particular area each. Their strength levels are relatively greater than EX viruses, with the first Rare version generally being between V2 and V3 in strength (like 2EX) and the second Rare being even stronger than the SP version. On top of that the Rare viruses tend to have extra abilities to put them at an even higher level, for instance RareMettool cracks panels it attacks and RareMettool2 creates swamp over its attacked panels. As the example suggests, the naming scheme simply takes the first family member's name and attaches "Rare" to the beginning, with the second version being "Rare(name)2", regardless of whether the rest of the family uses a numbered naming system. Exceptions are written out on the side.
These are the viruses introduced in EXE1. This was the only game not to display the virus names in battle, so a few don't have english names. I recently removed the made-up names I put in for no reason other than to loosely translate the Japanese ones although I forgot "Miner", and I'm too lazy to erase it right now so in case you're wondering that's not official.
Just in case you've never heard of them, "ArbalBoy" is derived from "Arbalest", a medieval crossbow, and "Ammonicule" is derived from "Ammonite", a shellfish with a spiraled shell, just like the virus.
Also, I grouped Rush together with his Support Unit buddies introduced as NaviCust programs in EXE3. That's the only case where I have more than just recolours in a virus family.
The HardHead family originally had the simple "1,2,3" naming pattern, but it was changed in EXE3 when their attacks became elemental. I decided to go with their elemental names. The Handy virus family also gets re-named in EXE5, originally, they were just Handy/Handies 1-3.
The english translation for EXE5 is a bit inconsistent with past games, so some viruses get two sets of english names. There were also a few BN5 e-reader cards named after viruses. You normally can't see them in the english version without cheating. I've noted which virus names get changed according to the E-Reader cards. Arbalboy's english name was first introduced in the BN5 E-Reader, but BN6 made it official.
In the Kabutank family, the grey "SP" on on the end was originally Kabutank3 in the first two games, but I guess they thought the dark colours were more befitting a Kabutank3EX. So the Kabutank3 shown here is a new one for EXE5.
EXE6 also made two new palletes for older viruses. EXE3's SwordinSP was red, but Capcom later got some kind of obsession with SP types being dark, so the new SwordinSP is black. The same can be said about the new MegaliaE, which is essentially MegaliaSP in this game.
Megaman Network Transmission introduced these "viruses" which were actually stage enemies from the classic Megaman games. Rather than make all new sprites in BN style for this gallery I took the lazy way out and used their original series sprites. I did have to recolour one of the Gabyools red however. The only exception is the last one, which I did make all by myself based on the mid-boss in Starman.exe's stage. I also came up with the clever english name for it.
These are the families introduced in BN2. The grey version of the Windbox family was called "Stormbox" in BN2/3, and was renamed "VaccuumFan3" in EXE4. In EXE5 there was a typo and it was named "WindBox3", even though there was already another virus with the same name. Either way that is one virus with a lot of names.
For the Dominerd family, EXE5 broke the trend by not making "CurzedEX" have the same colours as EXE3's "CurzSP", and instead introduced an all-new, all-black pallette. That's why it's the only one labeled as "3EX", while the one to the right is still labeled as "SP".
Once again, a few viruses get re-re-named in BN5.
Now here's something interesting. EXE6 has a virus that can't be encountered! It's RareFan, the grey and gold one at the end of the WindBox family. For some reason or another, likely a mistake by the programmers, there's no battle group with this virus in it. So how did I get the sprite? I owe it entirely to Terence Fergusson at GameFAQs who showed me how to hack the game just enough to put RareFan into it. If you have the english Falzar version rom and are using VisualBoyAdvance, under "Tools", open the "Memory Viewer", then go to 080B388F and change the 25 to a 36, and then RareFan will appear in one of the battles on ACDC HP in place of a Cattack. There are other ways to do it, but that's what worked for me. I'm sure someone will make a more conventional cheat code to reveal this dummied virus eventually.
Here's BN3's additions. Instead of "EX" versions for the LaLa family, BN4 added ones with all-new names, namely the grey Mute, the orange Horn, and the green SP. BN3 already had a grey SP, but with slightly different colours than the Mute introduced in BN4. I decided to keep it labeled as SP and stuck BN4's green version with the "1EX" marker.
The first game where the EX versions were introduced. The only exceptions here are the Weather and Elemperor families, which have relatively unique names for the first five versions rather than EX naming, just like with the LaLa family.
These are EXE5's viruses. Not many surprises here, but there were for viruses in past games. See above and you'll notice quite a few retro viruses got their original names forgotten for some reason. Dominerd and others keep their old names, so it's more like the translators consciously wanted to change the others...even though the new ones aren't much better, so confusing. The last three families are Dark Viruses, only encountered as mid-bosses in Liberation Mode. Apparently they're all special enough to get a number naming system.
And finally, the EXE6 viruses! The english translations were unusually uninspired this time. There haven't been this many "1,2,3" naming schemes since BN1, and in the Japanese version only a few old virus families were numbered that way. And somehow we still ended up with three new families with no changed names at all.
It may seem odd that with each family having exactly six versions in the last three games that the Kettle family only has four. Well there are six Kettles programmed into the game, but the other two are sorta just clones of others. There are two types of the first version, one that can be harmed only by fire-elemental attacks and the other can be hurt by any attack. The sixth is a clone of KettleSP, which doesn't seem to have any difference from the regular KettleSP that's used. Again, Terence was the one that explained to me how this data was stored.
Thanks go out to Josuke Midori for helping me interpret many of the Japanese version virus names.