Most powerful in terms of dissipation in a single package, probably those.
There are also SCRs, GCTs and other esoterica used in the power realm, which may be higher power but I'm not sure.
Most powerful in terms of a single die, most likely the SCRs or whatever. They can be made on single wafers. IGBTs don't have the greatest yields, or good enough matching over the die, so they are usually sawn up into pieces under 25mm or so. Medium sized modules (600-1800V, 300-2000A) are usually made of many dies, matched, connected in parallel, and bonded to a metallized ceramic base plate.
Most powerful in terms of linear amplification rather than gross switching capacity, probably BJTs. The current density can be quite high, though that can also lead to runaway (second breakdown), which is true of modern density MOSFETs as well (and probably quite true of IGBTs, but they are never rated for linear operation or pulses longer than 1ms). Though BJTs were available as power darlington modules back in the day (ca. 600V 300A capacities, and probably more -- but intended for switching only), probably the largest available (or useful) today are TO-264 packaged On Semi transistors (MJE29xxx or something like that?), a quad of them being good for maybe a kilowatt (or more with better cooling).
Most powerful in terms of sheer power density (watts per die area), probably something in SiC, because the operating temperature can be significantly higher -- you have to find a device packaged in something other than plastic to test that though. The dies themselves are also quite small (it's hard to grow good quality SiC and get good yields).
I don't think there's anything "smart" that can dissipate more, physically speaking -- metal film or foil on a ceramic substrate makes one hell of a resistor, but it doesn't "transist" very well! If you need both power handling and control, you're better off with a hybrid approach: switched resistors, or something like that.
Tim