Disclaimer: I'm not addicted to Candy Crush. Just helping my family member who plays it.
Of the levels I have played so far, Level 275 must be one of the toughest levels.
For those of you who are stuck at this level for eons, here's my strategy for clearing this level:
1) Take care not to trigger the bombs that are at the top two corners of the screen. Once triggered, they are almost impossible to get rid of. Instead, allow some layers of chocolate (1-3) to build up around it as a cushion/buffer.
2) Try to clear the jellies that are at the two sides and center of the screen. I find that clearing the sides first helps to keep the chocolates at bay i.e. control the chocolate growth, as well as to open up the area for playing.
3) Try to keep the fishes at the bottom for the last, as they can help by swimming towards the last few blocks that you find difficult to clear.
For me, I cleared Level 275 using the above strategy. As for special powers, I did use a (color bomb + striped candy) towards the end, when about 90% of the jellies have been cleared via the normal route. This triggered the bombs of course, but what was left after the (color bomb + striped candy) attack was easily cleared within the 2 counts provided by the bombs.
I hope the above helps somewhat. Of course, as with most of other Candy Crush games, luck plays an important role too!
