Need help removing iTunes photos from iPhone 6

See the following instructions from Keep your photos safely stored and up to date on all of your devices - Apple Support

If you don't want the synced photos on your iPhone, iPad, or iPod touch anymore, turn off syncing in iTunes and they'll be removed from your device. You can turn off syncing for some of your photo albums or all of them at once.

Stop syncing some albums

1. Open iTunes on your computer and connect your iPhone, iPad, or iPod touch.
2. Click on the device icon in iTunes.
3. Click Photos.
4. Choose "Selected albums" and deselect the albums or collections that you want to stop syncing.
5. Click Apply.

Stop syncing all photos

1. Open iTunes on your computer and connect your iPhone, iPad, or iPod touch.
2. Click on the device icon in iTunes.
3. Click Photos.
4. Deselect "Sync Photos" then click "Remove photos."
5. Click Apply.

Learn how to delete photos and videos synced from iTunes when you can't access the originals.

HOW TO DELETE ALL

PHOTOS FROM iPHONE 6

1. VISIT THESE TWO SITES
   
   1. VISIT Delete Photos on Your iPhone
   2. Update your iPhone to iOS 10 or Later (if need be):
      
2. OPEN PHOTOS APP
3. SELECT PHOTOS: Open: Photos Icon (On Far-Left of Bottom Menu Bar) > Go to: Moments Library (On Top Menu Bar)> Tap: Select (On Far-Right Corner of Top Menu Bar) > Tap: Select (On Right-Hand Side of Desired Date Row List)
4. SEND TO TRASH: Tap:Trashcan Icon (On Far-Right Corner of Bottom Menu Bar) > Select: Delete [number] Photos (On Bottom Pop-Up Menu)
5. DELETE ALL FROM TRASH: Tap: Albums Icon (On Far-Right of Bottom Menu Bar) > Tap: Recently Deleted Album > Tap: Select (On Far-Right Corner of Top Menu Bar) > Tap: Delete All Trash Icon (On Far-Right Corner of Bottom Menu Bar) > Tap: Delete [Number] Items (On Far-Top Bottom Menu Bar)

peerleader wrote:

HOW TO DELETE ALL

PHOTOS FROM iPHONE 6

1. VISIT THESE TWO SITES
   
   1. VISIT Delete Photos on Your iPhone
   2. Update your iPhone to iOS 10 or Later (if need be):
      
2. OPEN PHOTOS APP
3. SELECT PHOTOS: Open: Photos Icon (On Far-Left of Bottom Menu Bar) > Go to: Moments Library (On Top Menu Bar)> Tap: Select (On Far-Right Corner of Top Menu Bar) > Tap: Select (On Right-Hand Side of Desired Date Row List)
4. SEND TO TRASH: Tap:Trashcan Icon (On Far-Right Corner of Bottom Menu Bar) > Select: Delete [number] Photos (On Bottom Pop-Up Menu)
5. DELETE ALL FROM TRASH: Tap: Albums Icon (On Far-Right of Bottom Menu Bar) > Tap: Recently Deleted Album > Tap: Select (On Far-Right Corner of Top Menu Bar) > Tap: Delete All Trash Icon (On Far-Right Corner of Bottom Menu Bar) > Tap: Delete [Number] Items (On Far-Top Bottom Menu Bar)

Steps 2 through 5 will not work for photos that were synced to the phone from a computer. As indicated by the OP, there is no trashcan icon. See the following from Delete photos on your iPhone, iPad, and iPod touch - AppleSupport

If you add photos to your iPhone, iPad, or iPod touch from iTunes, you can't delete them directly from your device in the Photos app. Learn how to delete the photos from iTunes.