Which district in Singapore has the highest profitability?

Sure thing, Here are 20 projects with most number of profitable transactions.

Project Name	Tenure	Completion	No. of Units	Avg PSF*	Profitable Transactions
STIRLING RESIDENCES	99 yrs from 18/08/2017	2022	1,259	2,382	118
PARC ESTA	99 yrs from 12/07/2018	2022	1,399	2,296	115
JADESCAPE	99 yrs from 19/06/2018	2022	1,206	2,292	96
PENROSE	99 yrs from 03/07/2019	2024	566	2,140	89
Parc Clematis	99 yrs from 08/08/2019	2023	1,450	2,156	85
CLAVON	99 yrs from 07/10/2019	2024	640	2,080	68
Avenue South Residence	99 yrs from 14/08/2018	2023	1,074	2,254	57
PARK COLONIAL	99 yrs from 11/10/2017	2021	805	2,267	53
COMMONWEALTH TOWERS	99 yrs from 07/05/2013	2017	845	2,230	46
Queens Peak	99 yrs from 28/09/2015	2020	736	2,216	44
PRINCIPAL GARDEN	99 yrs from 21/07/2014	2018	663	2,174	43
Ki Residences At Brookvale	999 yrs from 23/03/1885	2024	660	2,199	42
THE WOODLEIGH RESIDENCES	99 yrs from 18/09/2017	2023	667	2,437	42
Seaside Residences	99 yrs from 18/04/2016	2021	841	2,363	38
THE POIZ RESIDENCES	99 yrs from 17/11/2014	2018	731	2,077	33
THE SAIL @ MARINA BAY	99 yrs from 12/08/2002	2008	1,111	2,120	32
Forett@bukit Timah	Freehold	2024	633	2,326	32
PARK PLACE RESIDENCES AT PLQ	99 yrs from 29/06/2015	2019	429	2,264	30
THE REEF AT KING'S DOCK	99 yrs from 12/01/2021	2024	429	2,539	28
J GATEWAY	99 yrs from 28/08/2012	2016	738	2,070	27

*Based on URA sales data in the last 12 months. Otherwise, based on latest transaction