The PROBA2 satellite was launched in November 2009, well in time to catch the first X-class flare of the new solar cycle (15 February 2011). The "X" in X-class flares stands for "eXtreme", and that's exactly what these flares are: the strongest class of rontgen flares that the Sun can produce.
Since then, various active regions on the Sun have produced a total of 45 X-class flares. All these were observed by the PROBA2's extreme ultraviolet (EUV) imager SWAP and its soft X-ray to mid-ultraviolet irradiance monitor LYRA, the 08 November 2013 flare being the sole exception. The folks from the PROBA2 team made a very nice collage of these events. For each X-class flare, they put a SWAP picture together with a LYRA graph. The astonishing result can be seen at the PROBA2's website. The must-see poster contains also additional information on flares and instruments, and was presented at the most recent ESWW13.
Forty-five X-class events for one solar cycle is not that much, compared to e.g. the 126 observed during the previous solar cycle (SC23). The last X-class event already dates back from 05 May 2015, that's 1.5 years ago! Though we are well in the declining phase of the current solar cycle, the emergence of a magnetically complex region remains possible, and thus a chance remains on one or a few X-class flares before the next cycle minimum. Above image shows SWAP's first X-class flare (15 February 2011; X2.2), and the image underneath shows the -for the moment- last observed X-class event (05 May 2015; X2.7).