Single target removal is hard to find on a budget for some colors. Evasion is also hard for certain colors (here's looking at you green). Here's a colorless card that handles both.
I have to thank Chris for turning me on to Predator Flagship. At just $0.34 on TCG Player at the time I wrote this, you get an artifact that can give your big dumb green creatures evasion and kill anything for 7 mana. Yes there is less mana intensive single target removal available in colorless, but those cards cost a lot more. This is also, repeatable single target removal. Sure it's mana intensive, but you're playing green and should have plenty of mana. The destroy feature can only work on flyers, but hey, you can just give them flying first.
SIMILAR CARDS
Beast within is great removal, targets any permanent, just gives a 3/3 beast. It is 6x as expensive and is only a one shot removal. Still a great card for a green deck looking to remove anything. I often pack one of these in addition to predator flagship. It doesn't offer any evasion to my creatures though, which my green decks often need.
Meteor golem is also cheap removal at $0.09 cents. Hits any nonland permanent giving you more flexibility. However, it's a one shot. Unless you're in a color with blink effects, you're not getting more than one thing with it. It also doesn't help your evasion. Still a great card that I use in a lot of green decks that need more removal. It's also pretty expensive, and the 3/3 body it gives you is not very useful.
DECKS THAT NEED THIS
I use this in my Gargos the Vicious Watcher deck. It gets my giant hydras past defenders and it can knock out targets that are too big for Gargos to fight.
It's also in my Krenko deck to help my reckless ones and other "gets bigger with more goblins" beaters past defenders. Red is also bad at removal of large creatures. Direct damage is not a great tool against 10/10s.
This is a great removal and evasion tool in colorless that works on two levels. There are plenty of decks that can use both these effects. Maybe it will help convince you to try mono-green. Join us on the happy big dumb creatures and mana dorks team. It's better once they can fly.