I think many of the respondants so far have confused "LAGgy good player" with "LAG."
Check-calling multiple streets hoping a good player is going to barrel off against someone who may be accused of being an OMC is not going to work.
I'll give an example of someone who may be reading this, and me as the LAG
. Villain noticed me being fairly active in late position - I raise CO wide and BTN very wide, and I 3-bet from those positions way more than anyone else (often more than the rest of the table combined). I open the CO to 4bb, he coldcalls OTB with Q5o. He has the right idea - as my range widens, so should his; but Q5o is just so awful that even if I raised 100% it's a mistake (I raise 25-30%). HU, flop is Q77tt (he has the BFD with the 5 if that matters). I bet about 2/3 pot, he calls. Again, he got one thing right - I'm cbetting a very high percentage here so he should call a very high percentage - but somehow this morphs into him expecting that I'm going to barrel off a 100% range and that top pair is low enough in his range to bluffcatch. Turn 9r, I check, and he checks behind, which is completely absurd - giving all my KT/KJ/JT hands free gutshot draws. River Jr, I make a 1/4 pot bet and he ... calls. On the face this doesn't appear absurd - he correctly believes I'm neither calling worse nor folding better if he raises - but only when I barrel a HUGE percentage does that work out for him, if I'm bluffing, top pair doesn't beat anything that A2 doesn't beat, so he's just condemned himself to calling a ridiculous percetange of his range.
He was also good enough to give me a tell which confirmed all this thinking - he tossed in a single chip at the end, thinking he was good for sure.
And he was, of course
- anything that beat him would have probably stacked him (I'm snap value betting QJ+ 3x for this exact reason). Basically he wins about 1/4 of his stack when I barrel off, and loses it all when I barrel.
If he wants to be the kind of person that gives me headaches, he needs to:
1. Show that he can play back preflop appropriately wide. If he 3-bets more than 20% there or less than 8%, I'm just raising with impunity.
2. Make thin value bets and raises on the flop. If I get to bet/fold because his raising range is crushing, then I have a really easy decision with weak made hands (like 88-JJ in this example).
3. Show up at showdown like he had a plan, something where even if I won, I'd think to myself, wow, that would not have worked out for 80% of my range, I won the pot but he pwned me.