Someone other than Napoleon goes on a 'path of conquest', in the 19th century.
Bonus points if the conquests last.
Bonus points if this doesn't happen in Europe or at least doesn't involve the French or Germans.
Bonus points if the path of conquest has little diplomatic justification but still succeeds anyway.
McClellan botches 1862 worse than OTL, CSA wins all states including, south, and east of TX, AR, TN, and VA (but no territories.) USA uses its army to invade Canada and eventually Mexico. USA manages to hold on to all of Canada, plus Sonora, Chihuahua, the Baja peninsula, Sinola, and Durango. CSA fragments due to infighting and economic issues, USA gobbles CSA piecemeal by 1900. Plausible, or ASB? I'm thinking a 1862 CSA victory is about 90% ASB, and being able to take/hold that much land rapidly equally so, though. So, I admit my theory here is 99% ASB by my own estimates.
Anything else I can think of requires too much handwavium, (outside of the aforementioned Brazil/Argentina South American sweep.)
If you're not talking continential-scale, but taking the concept of taking more territory than one currently has at the outset? PERHAPS Japan, but it would require an earlier Opening for a POD. Had Napoleon fizzled before starting his conquering spree, perhaps a "Nelson meets the Shoguns?"