Imagine the following made up scenario (see diagram for unit positions). Also note the Initiative values of the various units.

Purple Unit, (Monster) Initiative 9 and then ASL Thunderstomp
Green unit, Initiative 6 (Riders), Initiative 3 (mounts)
Red Unit, Initiative 5
Blue Unit, Initiative 4 (Riders), Initiative 3 (mounts)

Diagram A
Red unit is mutiple charged by Green & Purple Unit (Front) and Blue unit (Rear).
Green and Blue are cavalry (split profiles, mounts have different / lower Initiatives to the riders)
Purple is unit type Monster (has Thunderstomp)

Diagram B
Purple strikes first and kills 6 models – opponent removes 6 models, numbered 15 – 20 (does it make any difference if models 16 – 21 were removed?)
The riders from Green unit strike next, kills 6 models, reducing them to two models remaining no. 10 and 11 (champion & standard bearer)
Red unit goes next and gets to attack back at Green unit (I assume they can’t target Purple or Blue units at this stage?) but fails to kill any.

Diagram C
The next iniative step would have riders from blue to attack but they are no longer in B2B (checked BRB page 61 – shrinking units, multiple fights) so they ‘nudge’ into Red.
Only models 23, 24 and 25 are able to attack (22 is not in B2B) – they fail to kill any models from Red Unit – see BRB page 50 – split profiles / striking order
Next step has the ‘mounts’ from both Green and Blue units attacking – only 2, 3, 4, 23, 24 & 25 are able to attack (1 and 22 are not in B2B) – again see BRB page 50 – split profiles / striking order
The ‘mounts’ fail to kill any models from Red.
Last set of attacks are from the Purple unit in the form of ‘Thunderstomp’ – again unit must ‘nudge’ to the left (is this correct, does it follow rule on page 61 or rule on page 50?) – so as to maintain B2B and then attacks.