Which airline has highest amount of taxes/surcharges (YQ) for award tickets?
 

Well, round trip award ticket with SQ in Business, SIN-CPT-SIN not only cost me 76000 miles, but SGD 1050 (appx US $770) in addition with taxes and surcharges.

Just wonder, is there any airline which charges higher amount of taxes/surcharges for award tickets?

Probably BA on J/F tickets when you combine the fuel surcharges and the ex-UK higher rate APD

LAX-LHR return on BA in J is US$1238 (US$904 in YQ, remainder in other taxes/fees including APD).

Definitely BA in my experience;I found that it has almost always made more sense for me to buy a cheap revenue ticket than use miles; always felt that it was a hell of a waste to use >200k miles to redeem for a base fare that is under 2-3k on sale. Only really redeemed for CX and JL F redemptions for the unreasonable surcharges on BA. :(
But second place has to be SQ; but I have had some reasonable redemptions such as SQ JFK-SIN for 93.5k miles+ ~250 euros in surcharges. ^
SQ suggests that the surcharges are 268 SGD ex Singapore and ZAR 3240 ex-SA, not sure where those data points are coming from.

Doubt that it is just 250 euros (less than $300), considering that above mentioned round trip to South Africa is $770 and round trip to NZ is appx $650

BA

I've seen Y tickets on TATL routes with ~250€ YQ, 90€ base fare and the remaining 100 or 150€ in taxes and other charges.

That said, a high YQ is not necessarily bad on fully paid tickets. It doesn't make much of a difference whether you pay high base fares or high YQ. A high YQ is more of a concern when booking reward flights.

Currently I'm more concerned about airlines "eliminating" YQ/YR by integrating it into the base fare and once Jet A1 gets more expensive again, they will add a new YQ on top of the increased base fares.

LH group also is quite nasty...

This.

I attached a screenshot of the SQ redemption booking page
And your SIN-CPT-SIN
I couldn't grab the full booking; but you can see it.

I'd agree with BA as the worst.

Grrr... you are right. Somehow I was counting the amount I paid for two round trip award tickets in C. So one way it is SGD 270 from SIN to South Africa.