I think he indicated in the original post up top, that his problem was predators (namely fox). I think the .25 Sumatra plus pump is a little out of his price range, but for what he is asking the air rifle to do, he will need to spend the extra money to be happy.
What slugs I like to shoot, my favorite target, and small game slug is the 155grain EPP/UG SWC. I'd use that up to fox. For coyote (haven't hunted them yet), I am thinking I would like to use the 175grain .45Slim SWC due to it's larger meplat. I used an obsolete 226grain Lyman #45266 SWC to shoot an 80lb hog in the brain, and the 255grain PRS 250 (BigLube design) RFN to kill a corsican ram, shooting it thru the heart/lungs.
I like to increase meplat size along with the size of the quarry hunted. Not a big fan of roundnoses, or hollowpoints for hunting.
Oh, and just for fun I let my friend kill this book with a Lee 452252 weighing 260grains. It's .36 meplat demonstrates why I am a fan of the big meplat.