The TMDb rule is to keep the oldest, the smallest ID.

Kenneth MacDonald (I)
https://www.themoviedb.org/person/103357-kenneth-macdonald IMDB ID nm0531810
Credits: 74 = 1923 > 1967
https://www.imdb.com/name/nm0531810/ Kenneth MacDonald (I) (1901–1972) - Actor
Credits: 255 = 1923 > 1972

Kenneth MacDonald (II)
https://www.themoviedb.org/person/1212716-kenneth-macdonald IMDB ID nm0531811
Credits: 11 = 1957 > 2003
https://www.themoviedb.org/person/1263225-kenneth-macdonald IMDB ID nm1129390
Credits: 4 = 1980 > 1989
https://www.imdb.com/name/nm0531811/ Kenneth MacDonald (II) (1950–2001) - Actor | Music Department
Credits: 50 = 1966 > 2001

Kenneth MacDonald (III)
https://www.themoviedb.org/person/2078344-kenneth-macdonald
Credits: 3 = 1924 > 1926
https://www.imdb.com/name/nm1129390/ Kenneth MacDonald (III) - Actor
Credits: 22 = 1923 > 1928

Add image
Move credits
Move IMDB ID nm1129390 to Kenneth MacDonald (III)
Deleted https://www.themoviedb.org/person/1263225-kenneth-macdonald

Banana

Some Kenneth MacDonald (II) credits, ID 1212716, are wrong.
2003 The Last Detective — (1 episode)
1957 Meet McGraw — (1 episode)
I could not edit directly on TV Show.

TIP: If you want to force the line break, click Space 2 times and then click Enter. Just Space > Space > Enter.

Some Kenneth MacDonald (II) credits, ID 1212716, are wrong.

What do you mean?

Kenneth MacDonald (III) https://www.themoviedb.org/person/2078344-kenneth-macdonald

Are we sure this one is a real actor? He looks a bit different, but it's hard to tell:

https://images-na.ssl-images-amazon.com/images/I/71hJxTeMK5L.jpg
http://img.over-blog-kiwi.com/1/58/91/76/20171207/ob_096b7e_dynamite-dan.png

p.s. I removed the bad bios.

Kenneth MacDonald (II)
Source IMDB
Born: November 20, 1950 in Manchester, England, UK
Died: August 5, 2001 (age 50) in Hawaii, USA

In TMDb: 1957 - Meet McGraw — (1 episode)
In IMDB credits begin in 1966.
And they end in 2001. The year he died.
But here in TMDb has a credit of 2003.
2003 - The Last Detective — (1 episode) as Stephen Pierce

And the IMDB reports this credit, Meet McGraw, to Kenneth MacDonald (I)
https://www.themoviedb.org/person/103357-kenneth-macdonald IMDB ID nm0531810
https://www.imdb.com/name/nm0531810/ Kenneth MacDonald (I) (1901–1972) - Actor
The Adventures of McGraw (TV Series)
Sheriff Corin

• McGraw in Reno (1957) ... Sheriff Corin
  

I could not delete the credit. When it went into editing, the invited actors did not appear anymore.

Kenneth MacDonald (III)

I do not understand what you mean by Real Actor.
It exists here in TMDb and IMDB.

https://www.themoviedb.org/person/2078344-kenneth-macdonald
https://www.imdb.com/name/nm1129390/ Kenneth MacDonald (III) - Actor

Very strange.

If I click on the episode link that is in Kenneth MacDonald's profile.
https://www.themoviedb.org/person/1212716-kenneth-macdonald
1957 Meet McGraw — (1 episode)
I'm going to this page. Season 1 Episode 23. > https://www.themoviedb.org/tv/30959-meet-mcgraw/episode/23
Show him and 3 other guest actors. Angie Dickinson + Jack Hogan + Harry Landers
See here https://i.imgur.com/GDu7jaW.jpg

If I go to this episode (Season 1 Episode 23), starting on the TV Show page. I end on this other page.
https://www.themoviedb.org/tv/30959-meet-mcgraw/episode/23?language=en-US
There's only the other Kenneth MacDonald - Sheriff Corin
See here https://i.imgur.com/ZuzldHD.jpg

I am getting crazy?
Same TV Show, same Season 1, same Episode 23 > Two different pages.
Ghost Link?

About the years for credits. Its just the year of the first episode. Not the real year of the episode appearance. So Every Academy awards credit has Some super old year.

@alltimemarr

IMDB
https://www.imdb.com/title/tt0050038/ The Adventures of McGraw - TV Series (1957–1958) - 42 episodes, 1957-1958

TMDb
https://www.themoviedb.org/tv/30959-meet-mcgraw Meet McGraw (1957) - Last Season Season 1 - 1957 | 42 Episodes
Season 1 of Meet McGraw premiered on June 17, 1957.

The amount of episodes is the same, 42.
The problem is that I can not delete the wrong Kenneth MacDonald (II).
This credit belongs to Kenneth MacDonald (I).

oh then it's just a ghost credit, it happens some of the times, just ask travis to remove it! :)

I do not understand what you mean by Real Actor. It exists here in TMDb and IMDB.

I meant: are we sure it's a real person? Many IMDb profiles are duplicates or a mismatch of credits belonging to different actors.

But here in TMDb has a credit of 2003. 2003 - The Last Detective — (1 episode) as Stephen Pierce

The IMDb credit makes no sense: https://www.imdb.com/name/nm1320793 The same actor couldn't have played an old man and a little boy in stuff released in 2003.

I think our credit is good. You can see the actor for yourself here (he's the suspect): https://youtu.be/lGkbz1PWimA?t=1h9m7s and this is a more recent picture of the actor: https://c8.alamy.com/comp/G48P0H/actor-ken-macdonald-from-only-fools-and-horses-attends-the-funeral-G48P0H.jpg

The confusion of the IMDB is bigger, and worse.
There are Two: Kenneth MacDonald (I) and Kenneth McDonald (I):
https://www.imdb.com/name/nm0531810/ Kenneth MacDonald (I) (1901–1972) - Actor > Actor (255 credits)
https://www.imdb.com/name/nm1320793/ Kenneth McDonald (I) - Actor > Actor (2 credits)
The difference is MacD x McD
Our case is with what has already died, the MacD. Urgh!#&%
These Scots could make our lives easier.

IMDb is too much a mess to be helpful.

But FYI the pilot episode of The Last Detective was filmed in 2001 as a one-off drama that was initially planned to aired in the fall. But I guess they liked it enough to order a full first season. It's probably why it aired so late though.

Summing up:

This movie https://www.themoviedb.org/tv/19880-the-last-detective
Belongs to this guy https://www.themoviedb.org/person/1212716-kenneth-macdonald Kenneth MacDonald (II)

But from this movie https://www.themoviedb.org/tv/30959-meet-mcgraw Meet McGraw (1957) - Last Season Season 1 - 1957 | 42 Episodes
We need to pull this guy https://www.themoviedb.org/person/1212716-kenneth-macdonald Kenneth MacDonald (II)
And let this guy stay https://www.themoviedb.org/person/103357-kenneth-macdonald Kenneth MacDonald (I)

Bump: And let this people stay

Angie Dickinson, Jack Hogan, Harry Landers