Hero flopped a set of Jacks and played it aggressively out of position in a multiway pot — the line is strong throughout. The river call facing the all-in is correct given only 22 combos beat a set here; this is a cooler against the turned straight.
Street-by-Street Analysis
Preflop (7/10)
Calling $25 with JJ in the BB closing the action in a multiway pot is fine, though 3-betting for value to thin the field and build a pot in position-disadvantaged spot is the stronger play at 350 BB deep — you'd charge draws and narrow ranges.
Flop (8/10)
Leading $50 (half pot) into three opponents with a set of Jacks on A♥J♠8♦ is good — you extract value from Ax hands and draws while the board is unpaired and rainbow, and a donk-bet here can look like a blocking bet with a weak ace, encouraging action.
Turn (6/10)
Betting $100 (half pot) is reasonable, but when LJ raises to $350, just calling is the mistake. You have a set of Jacks — the third-best made hand possible — and you're 350 BB deep. A 3-bet to ~$850 builds the pot and charges QT (which just turned the nuts) and two-pair hands, while also defining LJ's range before a potentially scary river. Flatting lets every draw see a cheap river and keeps the pot small with a hand that wants stacks in.
River (8/10)
Betting $500 into $902 and then calling the all-in for $1,327 into a pot of $2,502 is correct. Only 22 combos beat you (3 sets of Aces, 3 sets of Kings, 16 straights with QT), while your set crushes the vast majority of value hands LJ could raise — AK, AJ, KJ, two pairs, and bluffs. You're getting roughly 2:1 and need to be good about a third of the time. Easy call.
Hindsight: LJ held Q♥T♣ for the turned Broadway straight. A turn 3-bet might not have changed the outcome — QT with the nuts would likely get it in regardless — but it would have been the higher-EV play against LJ's full range.
