De'vID:

Megatron qam bIngDaq Optimus Prime nach
chevlu'pu'bogh taptaHvIS, Megatron 'IH law' Hoch Decepticon 'IH puS.

there is something which rubs me the wrong way in this sentence.. lets
analyze it together..

first it says:
{Megatron qam bIngDaq Optimus Prime nach chevlu'pu'bogh taptaHvIS}
under the foot of megatron the head of optimus prime, which someone
had separated, while he was squashing

so, we are left to wonder "who was squashing that head ?" only to read
next the name of "megatron", which simultaneously is the first of the
two nouns in a law'/puS construction.

Is this correct ? Can the subject (if megatron is indeed the subject
of the first sentence), be at the same time the first noun of a
law'/puS construction ?

There is only one sentence here.

Megatron qam bIngDaq (locative phrase)
below Megatron's feet

Optimus Prime nach chevlu'pu'bogh taptaHvIS (subordinate "while" clause containing a relative clause)
while he squashes Optimus Prime's separated head

Megatron 'IH law' Hoch Decepticon 'IH puS (main clause)
Megatron is more beautiful than all Decepticons

The locative phrase is attached to the relative clause, not the main clause:

Megatron qam bIngDaq Optimus Prime nach chevlu'pu'bogh taptaHvIS
while he [Megatron] squashes Optimus Prime's separated head

The second instance of Megatron in the sentence is not the subject of the subordinate clause; it is only the first noun of the comparative clause. The subject of the subordinate clause is an elided ghaH. You have to work out from context that ghaH refers to Megatron (because who else would be squashing a severed head but the entity whose feet we are directed under?).

-- 
SuStel
http://trimboli.name